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smsc LAN8720A/LAN8720Ai revision 1.4 (08-23-12) datasheet datasheet product features LAN8720A/LAN8720Ai small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support highlights ? single-chip ethernet physical layer transceiver (phy) ? comprehensive flexpwr ? technology ? flexible power management architecture ? lvcmos variable i/o voltage range: +1.6v to +3.6v ? integrated 1.2v regulator ? hp auto-mdix support ? miniature 24-pin qfn lead-free rohs compliant package (4 x 4 x 0.85mm height). target applications ? set-top boxes ? networked printers and servers ? test instrumentation ? lan on motherboard ? embedded telecom applications ? video record/playback systems ? cable modems/routers ? dsl modems/routers ? digital video recorders ? ip and video phones ? wireless access points ? digital televisions ? digital media adaptors/servers ? gaming consoles ? poe applications (refer to smsc application note 17.18) key benefits ? high-performance 10/100 ethernet transceiver ? compliant with ieee802.3/802.3u (fast ethernet) ? compliant with iso 802-3/ieee 802.3 (10base-t) ? loop-back modes ? auto-negotiation ? automatic polarity detection and correction ? link status change wake-up detection ? vendor specific register functions ? supports the reduced pin count rmii interface ? power and i/os ? various low power modes ? integrated power-on reset circuit ? two status led outputs ? latch-up performance exceeds 150ma per eia/jesd 78, class ii ? may be used with a single 3.3v supply ? additional features ? ability to use a low cost 25mhz crystal for reduced bom ? packaging ? 24-pin qfn (4x4 mm) lead-free rohs compliant package with rmii ? environmental ? extended commercial temperature range (0c to +85c) ? industrial temperature range version available (-40c to +85c)
order numbers: LAN8720A-cp-tr for 24-pin qfn lead-free rohs compliant package (0 to +85c temp) LAN8720Ai-cp-tr for 24-pin qfn lead-free ro hs compliant package (-40 to +85c temp) reel size is 4,000. this product meets the halogen maximum concentration values per iec61249-2-21 for rohs compliance and environmen tal information, please visit www.smsc.com/rohs please contact your smsc sales representative fo r additional documentation related to this product such as application notes, anomaly sheets, and design guidelines. small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 2 smsc LAN8720A/LAN8720Ai datasheet copyright ? 2012 smsc or its subsidiaries. all rights reserved. circuit diagrams and other information relating to smsc produc ts are included as a means of illustrating typical applications. consequently, complete information sufficient for construction purposes is not necessarily given. although the information has been checked and is believed to be accurate, no re sponsibility is assumed for inaccuracies. smsc reserves the right to make changes to specifications and produc t descriptions at any time without notice. contact your local sm sc sales office to obtain the latest specifications before placing your product order. the provision of this inform ation does not convey to the purchaser of the described semicond uctor devices any licenses under any patent rights or other intellectual property rights of smsc or others. all sales are expressly conditional on your agreement to the te rms and conditions of the most recently dated version of smsc's standard terms of sale agreement dated before the date of your order (the "terms of sale agreement"). the pro duct may contain design defects or errors known as anomalies which may cause the product's functions to deviate from published specifications. anomaly sheets are availab le upon request. smsc products are not designed, intended, authorized or warranted for use in any life support or other application where product failure could cause or contribute to personal injury or severe property damage. any and all such uses without prior written approval of an officer of smsc and further testing and/or modification will be fully at the risk of the customer. copies of this document or other smsc literature, as well as the terms of sale agreement, may be obtained by visiting smsc?s website at h ttp://www.smsc.com. smsc is a registered trademark of standard microsystems corporat ion (?smsc?). product names and company na mes are the trademarks of their respective holders. the microchip name and logo, and the microchip logo are registered trademarks of microchip technology incorporated in the u.s.a . and other countries. smsc disclaims and excludes any and all warrant ies, including without limi tation any and all implied warranties of merchantabil ity, fitness for a particular purpose, title, a nd against infringement and the like, and any and all warranties arising from any cou rse of dealing or usage of trade. in no event shall smsc be liable for any direct, incidental, indi rect, special, punitive, or cons equential damages; or for lost data, profits, savings or revenues of any kind; regardless of the form of action, whether based on contrac t; tort; negligence of smsc or others; strict liability; breach of wa rranty; or otherwise; whether or not any remedy of buyer is h eld to have failed of its essential purpose, and whether or not smsc has been advised of the possibility of such damages.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 3 revision 1.4 (08-23-12) datasheet table of contents chapter 1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.1 general terms and conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2 general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 chapter 2 pin description and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1 pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.2 buffer types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 chapter 3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1 transceiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1.1 100base-tx transmit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1.2 100base-tx receive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.1.3 10base-t transmit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3.1.4 10base-t receive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.2 auto-negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.2.1 parallel detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.2 restarting auto-negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 5 3.2.3 disabling auto-negotiation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.4 half vs. full duplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.3 hp auto-mdix support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.4 mac interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.4.1 rmii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.5 serial management interface (smi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.6 interrupt management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.6.1 primary interrupt system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.6.2 alternate interrupt system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.7 configuration straps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.7.1 phyad[0]: phy address configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.7.2 mode[2:0]: mode configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.7.3 regoff: internal +1.2v regulato r configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.7.4 nintsel: nint/refclko configuratio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.8 miscellaneous functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.8.1 leds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.8.2 variable voltage i/o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.8.3 power-down modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 8 3.8.4 isolate mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.8.5 resets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.8.6 carrier sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.8.7 link integrity test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.8.8 loopback operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.9 application diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 3.9.1 simplified system level application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3.9.2 power supply diagram (1.2v supplied by internal regulator) . . . . . . . . . . . . . . . . . . . . 43 3.9.3 power supply diagram (1.2v supplied by external source). . . . . . . . . . . . . . . . . . . . . . 44 3.9.4 twisted-pair interface diagram (single power supply ). . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.9.5 twisted-pair interface diagram (dual power supplies) . . . . . . . . . . . . . . . . . . . . . . . . . 46 chapter 4 register descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.1 register nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.2 control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.2.1 basic control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 4 smsc LAN8720A/LAN8720Ai datasheet 4.2.2 basic status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.2.3 phy identifier 1 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.2.4 phy identifier 2 register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.2.5 auto negotiation advertisement regi ster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.2.6 auto negotiation link partner ability register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.2.7 auto negotiation expansion register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.2.8 mode control/status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.2.9 special modes register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.2.10 symbol error counter register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.2.11 special control/status i ndications register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.2.12 interrupt source flag register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.2.13 interrupt mask register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.2.14 phy special control/status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 chapter 5 operational characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5.1 absolute maximum ratings*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5.2 operating conditions** . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3 power consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3.1 ref_clk in mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3.2 ref_clk out mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 5.4 dc specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.5 ac specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 5.5.1 equivalent test load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 5.5.2 power sequence timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 5.5.3 power-on nrst & configuration strap timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 5.5.4 rmii interface timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.5.5 smi timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.6 clock circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 chapter 6 package outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 chapter 7 datasheet revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 5 revision 1.4 (08-23-12) datasheet list of figures figure 1.1 system block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 1.2 architectural overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 2.1 24-qfn pin assignments (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 3.1 100base-tx transmit data path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 3.2 100base-tx receive data path. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 3.3 relationship between received data and specific mii signals . . . . . . . . . . . . . . . . . . . . . . 21 figure 3.4 direct cable connection vs. cross-over cable conn ection . . . . . . . . . . . . . . . . . . . . . . . . . 26 figure 3.5 mdio timing and frame structure - read cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 3.6 mdio timing and frame structure - write cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 3.7 external 50mhz clock sources the ref_clk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 figure 3.8 sourcing ref_clk from a 25mhz crystal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 figure 3.9 sourcing ref_clk from external 25mhz source. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 figure 3.10 led1/regoff polarity configuratio n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 figure 3.11 led2/nintsel polarity configurat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 figure 3.12 near-end loopback block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 figure 3.13 far loopback block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 figure 3.14 connector loopback block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 figure 3.15 simplified system level applicatio n diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 figure 3.16 power supply diagram (1.2v supplied by internal re gulator) . . . . . . . . . . . . . . . . . . . . . . . 43 figure 3.17 power supply diagram (1.2v supplied by external s ource) . . . . . . . . . . . . . . . . . . . . . . . . . 44 figure 3.18 twisted-pair interface diagram (single power supply ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 figure 3.19 twisted-pair interfac e diagram (dual power supplies). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 figure 5.1 output equivalent test load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 figure 5.2 power sequence timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 figure 5.3 power-on nrst & configuration strap timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 figure 5.4 rmii timing (ref_clk out mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 figure 5.5 rmii timing (ref_clk in mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 figure 5.6 smi timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 6 smsc LAN8720A/LAN8720Ai datasheet list of tables table 2.1 rmii signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 table 2.2 led pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 table 2.3 serial management interface (smi) pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 table 2.4 ethernet pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 table 2.5 miscellaneous pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 table 2.6 analog reference pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 table 2.7 power pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 table 2.8 24-qfn package pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 table 2.9 buffer types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 table 3.1 4b/5b code table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 table 3.2 interrupt management table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 table 3.3 alternative interrupt system management table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 table 3.4 mode[2:0] bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 table 3.5 pin names for mode bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 table 3.6 nintsel configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 table 4.1 register bit types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 table 4.2 smi register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 table 5.1 device only current consum ption and power dissipation (ref_clk in mode) . . . . . . . . . . 64 table 5.2 device only current consumption and power dissipation (ref_clk out mode) . . . . . . . . . 65 table 5.3 non-variable i/o buffer characterist ics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 table 5.4 variable i/o buffer characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 table 5.5 100base-tx transceiver ch aracteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7 table 5.6 10base-t transceiver char acteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 table 5.7 power sequence timing values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 table 5.8 power-on nrst & configuration strap timing values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 table 5.9 rmii timing values (ref_clk out mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 table 5.10 rmii timing values (ref_clk in mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2 table 5.11 rmii clkin (ref_clk) timing values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 table 5.12 smi timing values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 table 5.13 crystal specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 table 7.1 customer revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 7 revision 1.4 (08-23-12) datasheet chapter 1 introduction 1.1 general terms and conventions the following is list of the general terms used throughout this document: 1.2 general description the LAN8720A/LAN8720Ai is a low-power 10base- t/100base-tx physical la yer (phy) transceiver with variable i/o voltage that is compli ant with the ieee 802.3-2005 standards. the LAN8720A/LAN8720Ai supports communication with an ethernet mac via a standard rmii interface. it contains a full-duplex 10-base- t/100base-tx transceiver and supports 10mbps (10base-t) and 100mbps (100base- tx) operation. the LAN8720A/LAN8720Ai implements auto- negotiation to automatically determine the best possible speed and duplex mode of operation. hp auto-mdix support allows the use of dire ct connect or cross-over lan cables. the LAN8720A/LAN8720Ai supports both ieee 802. 3-2005 compliant and vendor-specific register functions. however, no register access is requi red for operation. the initial configuration may be selected via the configuration pins as described in section 3.7, "configuration straps," on page 31 . register-selectable configuration options may be used to further define the functionality of the transceiver. per ieee 802.3-2005 standards, all digital interfac e pins are tolerant to 3.6v. the device can be configured to operate on a single 3.3v supply utilizing an integrated 3. 3v to 1.2v linear regulator. the linear regulator may be optionally disabled, allowing usage of a high efficiency external regulator for lower system powe r dissipation. the LAN8720A/LAN8720Ai is available in both ext ended commercial and industrial temperature range versions. a typical system application is shown in figure 1.1 . byte 8-bits fifo first in first out buffer; often used for elasticity buffer mac media access controller rmii tm reduced media independent interface tm n/a not applicable x indicates that a logic state is ?don?t care? or undefined. reserved refers to a reserved bit field or address. unless otherwise noted, reserved bits must always be zero for write operations. unless otherwise noted, values are not guaranteed when reading reserved bits. unless otherwise noted, do not read or write to reserved addresses. smi serial management interface
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 8 smsc LAN8720A/LAN8720Ai datasheet figure 1.1 system block diagram figure 1.2 architectural overview LAN8720A/ LAN8720Ai 10/100 ethernet mac rmii mode led transformer crystal or clock oscillator mdi rj45 rmii logic interrupt generator leds pll receiver dsp system: clock data recovery equalizer squeltch & filters analog-to- digital 10m rx logic 100m rx logic 100m pll 10m pll transmitter 10m transmitter 100m transmitter 10m tx logic 100m tx logic central bias phy address latches LAN8720A/LAN8720Ai rbias led1 nint xtal2 xtal1/clkin led2 management control mode control reset control mdix control hp auto-mdix rxp/rxn txp/txn txd[0:1] txen rxd[0:1] rxer crs_dv mdc mdio auto- negotiation rmiisel nrst mode[0:2] smi phyad0
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 9 revision 1.4 (08-23-12) datasheet chapter 2 pin description and configuration note: when a lower case ?n? is used at the beginning of the signal name, it indicates that the signal is active low. for example, nrst indica tes that the reset signal is active low. note: the buffer type for each signal is indicated in the buffer type column. a description of the buffer types is provided in section 2.2 . figure 2.1 24-qfn pin a ssignments (top view) vss note: exposed pad (vss) on bottom of package must be connected to ground smsc LAN8720A/LAN8720Ai 24 pin qfn (top view) mdio 1 2 3 4 5 6 7 8 9 10 11 12 18 17 16 15 14 13 24 23 22 21 20 19 vddcr xtal1/clkin xtal2 led1/regoff led2/nintsel vdd2a txd1 txd0 txen nrst nint/refclko mdc vdd1a txn txp rxn rxp rbias crs_dv/mode2 rxer/phyad0 vddio rxd0/mode0 rxd1/mode1
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 10 smsc LAN8720A/LAN8720Ai datasheet table 2.1 rmii signals num pins name symbol buffer type description 1 transmit data 0 txd0 vis the mac transmits data to the transceiver using this signal. 1 transmit data 1 txd1 vis the mac transmits data to the transceiver using this signal. 1 transmit enable txen vis (pd) indicates that valid transmission data is present on txd[1:0]. 1 receive data 0 rxd0 vo8 bit 0 of the 2 data bits that are sent by the transceiver on the receive path. phy operating mode 0 configuration strap mode0 vis (pu) combined with mode1 and mode2, this configuration strap sets the default phy mode. see note 2.1 for more information on configuration straps. note: refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional details. 1 receive data 1 rxd1 vo8 bit 1 of the 2 data bits that are sent by the transceiver on the receive path. phy operating mode 1 configuration strap mode1 vis (pu) combined with mode0 and mode2, this configuration strap sets the default phy mode. see note 2.1 for more information on configuration straps. note: refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional details. 1 receive error rxer vo8 this signal is asserted to indicate that an error was detected somewhere in the frame presently being transferred from the transceiver. phy address 0 configuration strap phyad0 vis (pd) this configuration strap sets the transceiver?s smi address. see note 2.1 for more information on configuration straps. note: refer to section 3.7.1, "phyad[0]: phy address configuration," on page 31 for additional information.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 11 revision 1.4 (08-23-12) datasheet note 2.1 configuration strap va lues are latched on pow er-on reset and system reset. configuration straps are identified by an underlined symbol name. signals that function as configuration straps must be augmented with an external resistor when connected to a load. refer to section 3.7, "configuration straps," on page 31 for additional information. 1 carrier sense / receive data valid crs_dv vo8 this signal is asserted to indicate the receive medium is non-idle. when a 10base-t packet is received, crs_dv is asse rted, but rxd[1:0] is held low until the sfd byte (10101011) is received. note: per the rmii standard, transmitted data is not looped back onto the receive data pins in 10base-t half-duplex mode. phy operating mode 2 configuration strap mode2 vis (pu) combined with mode0 and mode1, this configuration strap sets the default phy mode. see note 2.1 for more information on configuration straps. note: refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional details. table 2.2 led pins num pins name symbol buffer type description 1 led 1 led1 o12 link activity led indication. this pin is driven active when a valid link is detected and blinks when activity is detected. note: refer to section 3.8.1, "leds," on page 37 for additional led information. regulator off configuration strap regoff is (pd) this configuration strap is used to disable the internal 1.2v regulator. when the regulator is disabled, external 1.2v must be supplied to vddcr. ? when regoff is pulled high to vdd2a with an external resistor, the internal regulator is disabled. ? when regoff is floating or pulled low, the internal regulator is enabled (default). see note 2.2 for more information on configuration straps. note: refer to section 3.7.3, "regoff: internal +1.2v regula tor configuration," on page 32 for additional details. table 2.1 rmii si gnals (continued) num pins name symbol buffer type description
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 12 smsc LAN8720A/LAN8720Ai datasheet note 2.2 configuration strap va lues are latched on pow er-on reset and system reset. configuration straps are identified by an underlined symbol name. signals that function as configuration straps must be augmented with an external resistor when connected to a load. refer to section 3.7, "configuration straps," on page 31 for additional information. 1 led 2 led2 o12 link speed led indication. this pin is driven active when the operatin g speed is 100mbps. it is inactive when the operating speed is 10mbps or during line isolation. note: refer to section 3.8.1, "leds," on page 37 for additional led information. nint/ refclko function select configuration strap nintsel is (pu) this configuration strap selects the mode of the nint/refclko pin. ? when nintsel is floated or pulled to vdd2a, nint is selected for operation on the nint/refclko pin (default). ? when nintsel is pulled low to vss, refclko is selected for operation on the nint/refclko pin. see note 2.2 for more information on configuration straps. note: refer to see section 3.8.1.2, "nintsel and led2 polarity selection," on page 37 for additional information. table 2.3 serial manageme nt interface (smi) pins num pins name symbol buffer type description 1 smi data input/output mdio vis/ vod8 serial management interface data input/output 1 smi clock mdc vis serial management interface clock table 2.4 ethernet pins num pins name symbol buffer type description 1 ethernet tx/rx positive channel 1 txp aio transmit/receive positive channel 1 1 ethernet tx/rx negative channel 1 txn aio transmit/receive negative channel 1 table 2.2 led pins (continued) num pins name symbol buffer type description
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 13 revision 1.4 (08-23-12) datasheet 1 ethernet tx/rx positive channel 2 rxp aio transmit/receive positive channel 2 1 ethernet tx/rx negative channel 2 rxn aio transmit/receive negative channel 2 table 2.5 miscellaneous pins num pins name symbol buffer type description 1 external crystal input xtal1 iclk external crystal input external clock input clkin iclk single-ended clock oscillator input. note: when using a single ended clock oscillator, xtal2 should be left unconnected. 1 external crystal output xtal2 oclk external crystal output 1 external reset nrst vis (pu) system reset. this signal is active low. 1 interrupt output nint vod8 (pu) active low interrupt output. place an external resistor pull-up to vddio. note: refer to section 3.6, "interrupt management," on page 29 for additional details on device interrupts. note: refer to section 3.8.1.2, "nintsel and led2 polarity selection," on page 37 for details on how the nintsel configuration strap is used to determine the function of this pin. reference clock output refclko vo8 this optional 50mhz clock output is derived from the 25mhz crystal oscillator. refclko is selectable via the nintsel configuration strap. note: refer section 3.7.4.2, "ref_clk out mode," on page 34 for additional details. note: refer to section 3.8.1.2, "nintsel and led2 polarity selection," on page 37 for details on how the nintsel configuration strap is used to determine the function of this pin. table 2.4 ethernet pins (continued) num pins name symbol buffer type description
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 14 smsc LAN8720A/LAN8720Ai datasheet table 2.6 analog reference pins num pins name symbol buffer type description 1 external 1% bias resistor input rbias ai this pin requires connection of a 12.1k ohm (1%) resistor to ground. refer to the LAN8720A/LAN8720Ai reference schematic for connection information. note: the nominal voltage is 1.2v and the resistor will dissipate approximately 1mw of power. table 2.7 power pins num pins name symbol buffer type description 1 +1.6v to +3.6v variable i/o power vddio p +1.6v to +3.6 v variable i/o power refer to the LAN8720A/LAN8720Ai reference schematic for connection information. 1 +1.2v digital core power supply vddcr p supplied by the on-chip regulator unless configured for regulator off mode via the regoff configuration strap. refer to the LAN8720A/LAN8720Ai reference schematic for connection information. note: 1 uf and 470 pf decoupling capacitors in parallel to ground should be used on this pin. 1 +3.3v channel 1 analog port power vdd1a p +3.3v analog port power to channel 1 refer to the LAN8720A/LAN8720Ai reference schematic for connection information. 1 +3.3v channel 2 analog port power vdd2a p +3.3v analog port power to channel 2 and the internal regulator. refer to the LAN8720A/LAN8720Ai reference schematic for connection information. 1 ground vss p common ground. this exposed pad must be connected to the ground plane with a via array.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 15 revision 1.4 (08-23-12) datasheet 2.1 pin assignments table 2.8 24-qfn package pin assignments pin num pin name pin num pin name 1 vdd2a 13 mdc 2 led2/nintsel 14 nint/refclko 3led1/regoff 15 nrst 4 xtal2 16 txen 5 xtal1/clkin 17 txd0 6 vddcr 18 txd1 7rxd1/mode1 19 vdd1a 8rxd0/mode0 20 txn 9vddio21 txp 10 rxer/phyad0 22 rxn 11 crs_dv/mode2 23 rxp 12 mdio 24 rbias
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 16 smsc LAN8720A/LAN8720Ai datasheet 2.2 buffer types note: the digital signals are not 5v tolerant. refer to section 5.1, "absolute maximum ratings*," on page 63 for additional buffer information. note 2.3 sink and source capabilities are dependant on the vddio voltage. refer to section 5.1, "absolute maximum ratings*," on page 63 for additional information. table 2.9 buffer types buffer type description is schmitt-triggered input o12 output with 12ma sink and 12ma source vis variable voltage schmitt-triggered input vo8 variable voltage output with 8ma sink and 8ma source vod8 variable voltage open-drain output with 8ma sink pu 50ua (typical) internal pull-up. unless otherwis e noted in the pin description, internal pull- ups are always enabled. note: internal pull-up resistors prevent unconnected inputs from floating. do not rely on internal resistors to drive signals external to the device. when connected to a load that must be pulled high, an ex ternal resistor must be added. pd 50ua (typical) internal pull-down. unless ot herwise noted in the pin description, internal pull-downs are always enabled. note: internal pull-down resistors prevent unconnected inputs from floating. do not rely on internal resistors to drive signals ex ternal to the device. when connected to a load that must be pulled low, an external resistor must be added. ai analog input aio analog bi-directional iclk crystal oscillator input pin oclk crystal oscillator output pin p power pin
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 17 revision 1.4 (08-23-12) datasheet chapter 3 functional description this chapter provides functional descriptions of th e various device features. these features have been categorized into the following sections: ? transceiver ? auto-negotiation ? hp auto-mdix support ? mac interface ? serial management interface (smi) ? interrupt management ? configuration straps ? miscellaneous functions ? application diagrams 3.1 transceiver 3.1.1 100base-tx transmit the 100base-tx transmit data path is shown in figure 3.1 . each major block is explained in the following subsections. 3.1.1.1 100base-tx transmit data across the rmii interface the mac controller drives the transmit data onto the txd bus and asserts txen to indicate valid data. the data is latched by the transceiver?s rmii blo ck on the rising edge of ref_clk. the data is in the form of 2-bit wide 50mhz data. figure 3.1 100base-tx transmit data path mac tx driver mlt-3 converter nrzi converter 4b/5b encoder cat-5 rj45 25mhz by 5 bits nrzi mlt-3 mlt-3 mlt-3 scrambler and piso rmii 25mhz by 4 bits ext ref_clk pll rmii 50mhz by 2 bits mlt-3 magnetics 125 mbps serial
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 18 smsc LAN8720A/LAN8720Ai datasheet 3.1.1.2 4b/5b encoding the transmit data passes from the rmii block to th e 4b/5b encoder. this block encodes the data from 4-bit nibbles to 5-bit symbols (known as ?code-groups?) according to ta b l e 3 . 1 . each 4-bit data-nibble is mapped to 16 of the 32 possible code-groups. the remaining 16 code-groups are either used for control information or are not valid. the first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles, 0 through f. the remaining code-groups are given le tter designations with slashes on either side. for example, an idle code-group is /i/, a tr ansmit error code-group is /h/, etc. table 3.1 4b/5b code table code group sym receiver interpretation transmitter interpretation 11110 0 0 0000 data 0 0000 data 01001 1 1 0001 1 0001 10100 2 2 0010 2 0010 10101 3 3 0011 3 0011 01010 4 4 0100 4 0100 01011 5 5 0101 5 0101 01110 6 6 0110 6 0110 01111 7 7 0111 7 0111 10010 8 8 1000 8 1000 10011 9 9 1001 9 1001 10110 a a 1010 a 1010 10111 b b 1011 b 1011 11010 c c 1100 c 1100 11011 d d 1101 d 1101 11100 e e 1110 e 1110 11101 f f 1111 f 1111 11111 i idle sent after /t/r until txen 11000 j first nibble of ssd, translated to ?0101? following idle, else rxer sent for rising txen 10001 k second nibble of ssd, translated to ?0101? following j, else rxer sent for rising txen 01101 t first nibble of esd, causes de-assertion of crs if followed by /r/, else assertion of rxer sent for falling txen 00111 r second nibble of esd, causes deassertion of crs if following /t/, else assertion of rxer sent for falling txen 00100 h transmit error symbol sent for rising txer 00110 v invalid, rxer if during rxdv invalid
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 19 revision 1.4 (08-23-12) datasheet 3.1.1.3 scrambling repeated data patterns (especially the idle code-grou p) can have power spectral densities with large narrow-band peaks. scrambling the data helps eliminate these peaks and spread the signal power more uniformly over the entire channel bandwidth. this uniform spectral density is required by fcc regulations to prevent excessive emi fr om being radiated by the physical wiring. the seed for the scrambler is generated from the transceiver address, phyad , ensuring that in multiple-transceiver applications, such as repeat ers or switches, each transceiver will have its own scrambler sequence. the scrambler also performs the parallel in serial out conversion (piso) of the data. 3.1.1.4 nrzi and mlt-3 encoding the scrambler block passes the 5-bit wide parallel data to the nrzi converter where it becomes a serial 125mhz nrzi data stream. the nrzi is encoded to mlt-3. mlt-3 is a tri-level code where a change in the logic level represents a code bit ?1? and the logic output remaining at the same level represents a code bit ?0?. 3.1.1.5 100m transmit driver the mlt3 data is then passed to the analog transmitter, which drives the differential mlt-3 signal, on outputs txp and txn, to the twis ted pair media across a 1:1 ratio isolation transformer. the 10base- t and 100base-tx signals pass through the same transformer so that common ?magnetics? can be used for both. the transmit ter drives into the 100 impedance of the cat-5 cable. cable termination and impedance matching require external components. 3.1.1.6 100m phase lock loop (pll) the 100m pll locks onto reference clock and genera tes the 125mhz clock used to drive the 125 mhz logic and the 100base-tx transmitter. 11001 v invalid, rxer if during rxdv invalid 00000 v invalid, rxer if during rxdv invalid 00001 v invalid, rxer if during rxdv invalid 00010 v invalid, rxer if during rxdv invalid 00011 v invalid, rxer if during rxdv invalid 00101 v invalid, rxer if during rxdv invalid 01000 v invalid, rxer if during rxdv invalid 01100 v invalid, rxer if during rxdv invalid 10000 v invalid, rxer if during rxdv invalid table 3.1 4b/5b code table (continued) code group sym receiver interpretation transmitter interpretation
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 20 smsc LAN8720A/LAN8720Ai datasheet 3.1.2 100base-tx receive the 100base-tx receive data path is shown in figure 3.2 . each major block is explained in the following subsections. 3.1.2.1 100m receive input the mlt-3 from the cable is fed into the transceiver (on inputs rxp and rxn) via a 1:1 ratio transformer. the adc samples the incoming different ial signal at a rate of 125m samples per second. using a 64-level quanitizer, it generates 6 digital bits to represent each sample. the dsp adjusts the gain of the adc according to the observed signal le vels such that the full dynamic range of the adc can be used. 3.1.2.2 equalizer, baseline wander correction and clock and data recovery the 6 bits from the adc are fed into the dsp bl ock. the equalizer in the dsp section compensates for phase and amplitude distortion caused by the ph ysical channel consisting of magnetics, connectors, and cat- 5 cable. the equalizer can restore the signal for any good-quality cat-5 cable between 1m and 150m. if the dc content of the signal is such that the low-frequency comp onents fall below the low frequency pole of the isolation transformer, then the dro op characteristics of t he transformer will become significant and baseline wander (blw) on the receiv ed signal will result. to prevent corruption of the received data, the transceiver corrects for blw and can receive the ansi x3.263-1995 fddi tp-pmd defined ?killer packet? with no bit errors. the 100m pll generates multiple phas es of the 125mhz clock. a mult iplexer, controlled by the timing unit of the dsp, selects the optimum phase for sa mpling the data. this is used as the received recovered clock. this clock is used to ex tract the serial data from the received signal. figure 3.2 100base-tx receive data path mac a/d converter mlt-3 converter nrzi converter 4b/5b decoder magnetics cat-5 rj45 pll rmii 50mhz by 2 bits 25mhz by 5 bits nrzi mlt-3 mlt-3 mlt-3 6 bit data descrambler and sipo 125 mbps serial dsp: timing recovery, equalizer and blw correction mlt-3 rmii 25mhz by 4 bits ext ref_clk
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 21 revision 1.4 (08-23-12) datasheet 3.1.2.3 nrzi and mlt-3 decoding the dsp generates the mlt-3 recovered levels that are fed to the mlt-3 converter. the mlt-3 is then converted to an nrzi data stream. 3.1.2.4 descrambling the descrambler performs an inverse function to t he scrambler in the transmitter and also performs the serial in parallel out (sipo) conversion of the data. during reception of idle (/i/) symbols. the descrambler synchron izes its descrambler key to the incoming stream. once synchronizati on is achieved, the descrambler locks on this key and is able to descramble incoming data. special logic in the descrambler ensures synchroniza tion with the remote transceiver by searching for idle symbols within a window of 4000 bytes (40us). this window ensures that a maximum packet size of 1514 bytes, allowed by the ieee 802.3 standard, can be received with no interference. if no idle- symbols are detected within this time-period, rece ive operation is aborted and the descrambler re-starts the synchronization process. 3.1.2.5 alignment the de-scrambled signal is then aligned into 5-bit code-groups by recognizing the /j/k/ start-of-stream delimiter (ssd) pair at the start of a packet. once the code-word alignment is determined, it is stored and utilized until the next start of frame. 3.1.2.6 5b/4b decoding the 5-bit code-groups are translated into 4-bit da ta nibbles according to the 4b/5b table. the translated data is presented on th e rxd[1:0] signal lines. the ssd, /j/k/, is translated to ?0101 0101? as the first 2 nibbles of the mac preamble. recepti on of the ssd causes the transceiver to assert the receive data valid signal, indicating that valid data is available on the rxd bus. successive valid code- groups are translated to data nibbles. reception of either the end of stream delimiter (esd) consisting of the /t/r/ symbols, or at least two /i/ symbols ca uses the transceiver to de -assert the carrier sense and receive data valid signals. note: these symbols are not translated into data. 3.1.2.7 receive data valid signal the receive data valid signal (rxdv) indicates that recovered and decoded nibbles are being presented on the rxd[1:0] outputs synchronous to rxclk. rxdv becomes active after the /j/k/ delimiter has been recognized and rxd is aligned to nibble boundaries. it remains active until either the /t/r/ delimiter is recognized or link test indicates failure or sigdet becomes false. rxdv is asserted when the first nibble of tran slated /j/k/ is ready for transfer over the media independent interface (mii mode). figure 3.3 relationship between recei ved data and specific mii signals 5d 5 data data data data rxd rx_dv rx_clk 5d 5 data data data data clear-text 5 jk 5 55 tr idle
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 22 smsc LAN8720A/LAN8720Ai datasheet 3.1.2.8 receiver errors during a frame, unexpected code-groups are consid ered receive errors. expected code groups are the data set (0 through f), and the /t/r/ (esd) symbol pair. when a receive error occurs, the rxer signal is asserted and arbitrary data is driven onto the rxd[1:0] lines. should an error be detected during the time that the /j/k/ delim iter is being decoded (bad ssd error), rxer is asserted true and the value ?1110? is driven onto the rxd[1:0] lines. note that the valid data signal is not yet asserted when the bad ssd error occurs. 3.1.2.9 100m receive data across the rmii interface the 2-bit data nibbles are sent to the rmii block. these data nibbles are clocked to the controller at a rate of 50mhz. the controller samples the data on the rising edge of xtal1/clkin (ref_clk). to ensure that the setup and hold r equirements are met, the nibbles ar e clocked out of the transceiver on the falling edge of xtal1/clkin (ref_clk). 3.1.3 10base-t transmit data to be transmitted comes from the mac laye r controller. the 10base-t transmitter receives 4-bit nibbles from the mii at a rate of 2.5mhz and converts them to a 10mbps serial data stream. the data stream is then manchester-encoded and sent to the analog transmitter, which drives a signal onto the twisted pair via the external magnetics. the 10m transmitter uses the following blocks: ? mii (digital) ? tx 10m (digital) ? 10m transmitter (analog) ? 10m pll (analog) 3.1.3.1 10m transmit data across the rmii interface the mac controller drives the transmit data onto th e txd bus. txd[1:0] shall transition synchronously with respect to ref_clk. when txen is asserted, txd[1:0] are accepted for transmission by the device. txd[1:0] shall be ?00? to indicate idle when txen is deasserted. values of txd[1:0] other than ?00? when txen is deasserted are reserved fo r out-of-band signalling (to be defined). values other than ?00? on txd[1:0] while txen is deasserted shall be ignored by the device.txd[1:0] shall provide valid data for each ref_clk period while txen is asserted. in order to comply with legacy 10base-t mac/contro llers, in half-duplex mode the transceiver loops back the transmitted data, on the receive path. th is does not confuse the mac/controller since the col signal is not asserted during this time. the tr ansceiver also supports the sqe (heartbeat) signal. 3.1.3.2 manchester encoding the 4-bit wide data is sent to the 10m tx block. the nibbles are converted to a 10mbps serial nrzi data stream. the 10m pll locks onto the external cl ock or internal oscillator and produces a 20mhz clock. this is used to manchester encode the nrz data stream. when no data is being transmitted (txen is low), the 10m tx block outputs normal link pulses (nlps) to maintain communications with the remote link partner. 3.1.3.3 10m transmit drivers the manchester encoded data is sent to the anal og transmitter where it is shaped and filtered before being driven out as a differential signal across the txp and txn outputs.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 23 revision 1.4 (08-23-12) datasheet 3.1.4 10base-t receive the 10base-t receiver gets the manchester- encoded analog signal from the cable via the magnetics. it recovers the receive clock from the signal and uses this clock to recover the nrzi data stream. this 10m serial data is converted to 4-bit data nibbles which are passed to the controller via mii at a rate of 2.5mhz. this 10m receiver uses the following blocks: ? filter and squelch (analog) ? 10m pll (analog) ? rx 10m (digital) ? mii (digital) 3.1.4.1 10m receive input and squelch the manchester signal from the cable is fed into t he transceiver (on inputs rxp and rxn) via 1:1 ratio magnetics. it is first filtered to reduce any out-of-band noise. it then passes through a squelch circuit. the squelch is a set of amplitude and timi ng comparators that norma lly reject differential voltage levels below 300mv and detect and re cognize differential voltages above 585mv. 3.1.4.2 manchester decoding the output of the squelch goes to the 10m rx block where it is validated as manchester encoded data. the polarity of the signal is also checked. if the polarity is reversed (local rxp is connected to rxn of the remote partner and vice versa), the condition is identified and corrected. the reversed condition is indicated by the xpol bit of the special control/status indications register . the 10m pll is locked onto the received manchester signal, fr om which the 20mhz cock is generated. using this clock, the manchester encoded dat a is extracted and converted to a 10mhz nrzi data stream. it is then converted from serial to 4-bit wide parallel data. the 10m rx block also detects valid 10base-t idle signals - normal link pulses (nlps) - to maintain the link. 3.1.4.3 10m receive data ac ross the rmii interface the 2-bit data nibbles are sent to the rmii block. these data nibbles are valid on the rising edge of the rmii ref_clk. 3.1.4.4 jabber detection jabber is a condition in which a station transmits for a period of time longer than the maximum permissible packet length, usually due to a fault condition, which results in holding the txen input for a long period. special logic is used to detect the jabber state and abort the transmission to the line within 45ms. once txen is deasserted, the logic resets the jabber condition. as shown in section 4.2.2, "basic stat us register," on page 50 , the jabber detect bit indicates that a jabber condition was detected. 3.2 auto-negotiation the purpose of the auto-negotiation function is to automatically configure the transceiver to the optimum link parameters based on the capabilitie s of its link partner. auto-negotiation is a mechanism for exchanging configuration information between tw o link-partners and automatically selecting the highest performance mode of operat ion supported by both sides. auto-negotiation is fully defined in clause 28 of the ieee 802.3 specification. once auto-negotiation has completed, information ab out the resolved link can be passed back to the controller via the serial management interface (smi). the results of the negotiation process are
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 24 smsc LAN8720A/LAN8720Ai datasheet reflected in the speed indication bits of the phy special control/status register , as well as in the auto negotiation link partner ability register . the auto-negotiation protocol is a purely physical layer activity and proceeds independently of the mac controller. the advertised capabilities of the transceiver are stored in the auto negotiation advertisement register . the default advertised by the transceiver is determined by user-defined on-chip signal options. the following blocks are activated during an auto-negotiation session: ? auto-negotiation (digital) ? 100m adc (analog) ? 100m pll (analog) ? 100m equalizer/blw/clock recovery (dsp) ? 10m squelch (analog) ? 10m pll (analog) ? 10m transmitter (analog) when enabled, auto-negotiation is started by t he occurrence of one of the following events: ? hardware reset ? software reset ? power-down reset ? link status down ? setting the restart auto-negotiate bit of the basic control register on detection of one of these events, the transceiv er begins auto-negotiation by transmitting bursts of fast link pulses (flp), which are bursts of link pulses from the 10m transmitter. they are shaped as normal link pulses and can pass uncorrupted down cat-3 or cat-5 cable. a fast link pulse burst consists of up to 33 pulses. the 17 odd-number ed pulses, which are always present, frame the flp burst. the 16 even-numbered pulses, which may be present or absent, cont ain the data word being transmitted. presence of a data pulse repres ents a ?1?, while absence represents a ?0?. the data transmitted by an flp burst is known as a ?link code word.? these are defined fully in ieee 802.3 clause 28. in summary, the transceiver advertise s 802.3 compliance in its selector field (the first 5 bits of the link code word). it advertises its technology ability according to the bits set in the auto negotiation advertisement register . there are 4 possible matches of the technology ab ilities. in the order of priority these are: ? 100m full duplex (highest priority) ? 100m half duplex ? 10m full duplex ? 10m half duplex (lowest priority) if the full capabilities of the transc eiver are advertised (100m, full duplex), and if the link partner is capable of 10m and 100m, then auto-negotiation selects 100m as the highest performance mode. if the link partner is capable of half and full duplex modes, then auto-negotiation selects full duplex as the highest performance operation. once a capability match has been determined, the link code words are repeated with the acknowledge bit set. any difference in the main content of the link code words at this time will cause auto-negotiation to re-start. auto-negotiation will also re-start if not all of the required flp bursts are received. the capabilities advertised during auto-negotiation by the transceiver are initially determined by the logic levels latched on the mode[2:0] configuration straps after reset completes. these configuration straps can also be used to disable auto-negotiation on power-up. refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional information.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 25 revision 1.4 (08-23-12) datasheet writing the bits 8 through 5 of the auto negotiation advertisement register allows software control of the capabilities advertised by the transceiver. writing the auto negotiation advertisement register does not automatically re-s tart auto-negotiation. the restart auto-negotiate bit of the basic control register must be set before the new abilities will be ad vertised. auto-negotiation can also be disabled via software by clearing the auto-negotiation enable bit of the basic control register . note: the device does not support ?next page? capability. 3.2.1 parallel detection if the LAN8720A/LAN8720Ai is connected to a device lacking the ability to auto-negotiate (i.e. no flps are detected), it is able to determine the speed of the link based on either 100m mlt-3 symbols or 10m normal link pulses. in this case the link is presumed to be half duplex per the ieee standard. this ability is known as ?parallel detection.? th is feature ensures interoperability with legacy link partners. if a link is formed via parallel detection, then the link partner auto-negotiation able bit of the auto negotiation expansion register is cleared to indicate that the link partner is not capable of auto- negotiation. the controller has access to this information via the management interface. if a fault occurs during parallel detection, the parallel detection fault bit of link partner auto-negotiation able is set. auto negotiation link partner ability register is used to store the link partner ability information, which is coded in the received flps. if the link partner is not auto-negotiation capable, then the auto negotiation link partner ability register is updated after completion of parallel detection to reflect the speed capability of the link partner. 3.2.2 restarting auto-negotiation auto-negotiation can be restarted at any time by setting the restart auto-negotiate bit of the basic control register . auto-negotiation will also restart if the link is broken at any time. a broken link is caused by signal loss. this may occur because of a cable break, or because of an interruption in the signal transmitted by the link partner. auto-negotiation resumes in an attempt to determine the new link configuration. if the management entity re-starts auto-negotiation by setting the restart auto -negotiate bit of the basic control register , the LAN8720A/LAN8720Ai will respond by stopping all transmission/receiving operations. once the break_link_timer is comp leted in the auto-negotiation state-machine (approximately 1200ms), auto-negotiation will re-star t. in this case, the link partner will have also dropped the link due to lack of a received signal, so it too will resume auto-negotiation. 3.2.3 disabling auto-negotiation auto-negotiation can be disabled by setting the auto-negotiation enable bit of the basic control register to zero. the device will then force its speed of operation to reflect the information in the basic control register ( speed select bit and duplex mode bit). these bits should be ignored when auto- negotiation is enabled. 3.2.4 half vs. full duplex half duplex operation relies on the csma/cd (carrier sense multiple access / collision detect) protocol to handle network traffic and collisions. in this mode, the carrier sense signal, crs, responds to both transmit and receive activity. if data is rece ived while the transceiver is transmitting, a collision results. in full duplex mode, the transceiver is able to trans mit and receive data simultaneously. in this mode, crs responds only to receive activity. the csma/cd protocol does not apply and collision detection is disabled.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 26 smsc LAN8720A/LAN8720Ai datasheet 3.3 hp auto-mdix support hp auto-mdix facilitates the use of cat-3 (10base-t) or cat-5 (100base-t) media utp interconnect cable without considerat ion of interface wiring scheme. if a user plugs in either a direct connect lan cable, or a cross-over patch cable, as shown in figure 3.4 , the device?s auto-mdix transceiver is capable of configuring the txp/txn and rxp/rxn pins for correct transceiver operation. the internal logic of the device detects the tx and rx pins of the connecting device. since the rx and tx line pairs are interchangeable, special pcb design considerations are needed to accommodate the symmetrical magnetics and termination of an auto-mdix design. the auto-mdix function can be disabled via the amdixctrl bit in the special control/status indications register . figure 3.4 direct cable connection vs. cross-over cable connection 1 2 3 4 5 6 7 8 txp txn rxp not used not used rxn not used not used 1 2 3 4 5 6 7 8 txp txn rxp not used not used rxn not used not used direct connect cable rj-45 8-pin straight-through for 10base-t/100base-tx signaling 1 2 3 4 5 6 7 8 txp txn rxp not used not used rxn not used not used 1 2 3 4 5 6 7 8 txp txn rxp not used not used rxn not used not used cross-over cable rj-45 8-pin cross-over for 10base-t/100base-tx signaling
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 27 revision 1.4 (08-23-12) datasheet 3.4 mac interface 3.4.1 rmii the device supports the low pin count reduced m edia independent interface (rmii) intended for use between ethernet transceive rs and switch asics. un der ieee 802.3, an mii co mprised of 16 pins for data and control is defined. in devices incorporat ing many macs or transceiver interfaces such as switches, the number of pins can add significant cost as the port co unts increase. rmii reduces this pin count while retaining a management interfac e (mdio/mdc) that is identical to mii. the rmii interface has the following characteristics: ? it is capable of supporting 10mbps and 100mbps data rates ? a single clock reference is used for both transmit and receive ? it provides independent 2-bit (di-bit) wide transmit and receive data paths ? it uses lvcmos signal levels, compatib le with common digital cmos asic processes the rmii includes the following interface signals (1 optional): ? transmit data - txd[1:0] ? transmit strobe - txen ? receive data - rxd[1:0] ? receive error - rxer (optional) ? carrier sense - crs_dv ? reference clock - (rmii references usually define this signal as ref_clk) 3.4.1.1 crs_dv - carrier sense/receive data valid the crs_dv is asserted by the device when the receive medium is non-idle. crs_dv is asserted asynchronously on detection of carrier due to the cr iteria relevant to the operating mode. in 10base- t mode when squelch is passed, or in 100base-x mode when 2 non-contiguous zeroes in 10 bits are detected, the carrier is said to be detected. loss of carrier shall result in the deassertion of crs_dv synchronous to the cycle of ref_clk which presents the first di-bit of a nibble onto rxd[1:0] (i.e. crs_dv is deasserted only on nibble boundaries). if the device has additional bits to be presented on rxd[1:0] following the initial deassertion of crs_dv, then the device shall asse rt crs_dv on cycles of ref_clk which present the second di-bit of each nibble and de-assert crs _dv on cycles of ref_clk which present the first di-bit of a nibble. the result is, starting on nibble boundaries, crs_dv toggles at 25 mhz in 100mbps mode and 2.5 mhz in 10mbps mode when crs ends before rxdv (i.e. the fifo still has bits to transfer when the carrier event ends). therefor e, the mac can accurately recover rxdv and crs. during a false carrier event, crs_dv shall remain asserted for the duration of carrier activity. the data on rxd[1:0] is considered valid once crs_dv is as serted. however, since the assertion of crs_dv is asynchronous relative to ref_clk, the data on rxd[1:0] shall be ?00? until proper receive signal decoding takes place. 3.4.1.2 reference clock (ref_clk) the rmii ref_clk is a continuous clock that provi des the timing reference for crs_dv, rxd[1:0], txen, txd[1:0] and rxer. the device uses ref_clk as the network clock such that no buffering is required on the transmit data path. however, on the receive data path, the receiver recovers the clock from the incoming data stream, and the devic e uses elasticity buffering to accommodate for differences between the recovered clock and the local ref_clk.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 28 smsc LAN8720A/LAN8720Ai datasheet 3.5 serial manageme nt interface (smi) the serial management interface is used to cont rol the device and obtain its status. this interface supports registers 0 through 6 as required by claus e 22 of the 802.3 standard, as well as ?vendor- specific? registers 16 to 31 allow ed by the specification. non-support ed registers (such as 7 to 15) will be read as hexadecimal ?ffff?. device registers are detailed in chapter 4, "register descriptions," on page 47 . at the system level, smi provides 2 signals: mdio and mdc. the mdc signal is an aperiodic clock provided by the station management controller (smc ). mdio is a bi-directional data smi input/output signal that receives serial data (commands) from the controller smc and sends serial data (status) to the smc. the minimum time between edges of th e mdc is 160 ns. there is no maximum time between edges. the minimum cycle ti me (time between two consecutiv e rising or two consecutive falling edges) is 400 ns. these modest timing requirement s allow this interface to be easily driven by the i/o port of a microcontroller. the data on the mdio line is latched on the rising edge of the mdc. the frame structure and timing of the data is shown in figure 3.5 and figure 3.6 . the timing relationships of the mdio signals are further described in section 5.5.5, "smi timing," on page 73 . figure 3.5 mdio timing and frame structure - read cycle figure 3.6 mdio timing and frame structure - write cycle mdc mdio read cycle ... 32 1's 0110a4a3a2a1a0r4r3r2r1r0 d1 ... d15 d14 d0 preamble start of frame op code phy address register address turn around data data from phy data to phy mdc mdio ... 32 1's 0 1 1 0 a4a3a2a1a0r4r3r2r1r0 write cycle d15 d14 d1 d0 ... data preamble start of frame op code phy address register address turn around data to phy
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 29 revision 1.4 (08-23-12) datasheet 3.6 interrupt management the device management interface supports an interrupt capability that is not a part of the ieee 802.3 specification. this interrupt capability generates an active low asynchronous interrupt signal on the nint output whenever certain events are detected as setup by the interrupt mask register . the device?s interrupt system pr ovides two modes, a primary in terrupt mode and an alternative interrupt mode. both systems will assert the nint pin low when the corresponding mask bit is set. these modes differ only in how they de-assert the nint interrupt output. these modes are detailed in the following subsections. note: the primary interrupt mode is the default interrupt mode after a power-up or hard reset. the alternative interrupt mode requires setup after a power-up or hard reset. 3.6.1 primary interrupt system the primary interrupt system is the default interrupt mode ( altint bit of the mode control/status register is ?0?). the primary interrupt system is always selected after power-up or hard reset. in this mode, to set an interrupt, set the corresponding mask bit in the interrupt mask register (see table 3.2 ). then when the event to assert nint is true, th e nint output will be asserted. when the corresponding event to deassert nint is true, then the nint will be de-asserted. note 3.1 if the mask bit is enabled and nint has been de-asserted while energyon is still high, nint will assert for 256 ms, approximately one second after energyon goes low when the cable is unplugged. to prevent an unexpected assertion of nint, the energyon interrupt mask should always be cleared as part of the energyon interrupt service routine. table 3.2 interrupt management table mask interrupt source flag interrupt source event to assert nint event to de-assert nint 30.7 29.7 energyon 17.1 energyon rising 17.1 ( note 3.1 ) falling 17.1 or reading register 29 30.6 29.6 auto-negotiation complete 1.5 auto-negotiate complete rising 1.5 falling 1.5 or reading register 29 30.5 29.5 remote fault detected 1.4 remote fault rising 1.4 falling 1.4, or reading register 1 or reading register 29 30.4 29.4 link down 1.2 link status falling 1.2 reading register 1 or reading register 29 30.3 29.3 auto-negotiation lp acknowledge 5.14 acknowledge rising 5.14 falling 5.14 or read register 29 30.2 29.2 parallel detection fault 6.4 parallel detection fault rising 6.4 falling 6.4 or reading register 6, or reading register 29 or re-auto negotiate or link down 30.1 29.1 auto-negotiation page received 6.1 page received rising 6.1 falling of 6.1 or reading register 6, or reading register 29 re-auto negotiate, or link down.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 30 smsc LAN8720A/LAN8720Ai datasheet note: the energyon bit in the mode control/status register is defaulted to a ?1? at the start of the signal acquisition process, therefore the int7 bit in the interrupt mask register will also read as a ?1? at power-up. if no signal is present, then both energyon and int7 will clear within a few milliseconds. 3.6.2 alternate interrupt system the alternate interrupt system is enabled by setting the altint bit of the mode control/status register to ?1?. in this mode, to set an interrupt, set the corresponding bit of the in the mask register 30, (see table 3.3 ). to clear an interrupt, either clear the corresponding bit in the interrupt mask register to deassert the nint output, or clear the interrupt source, and write a ?1? to the corresponding interrupt source flag. writing a ?1? to the interrupt source flag will cause the state machine to check the interrupt source to determine if the interrupt source flag should clear or stay as a ?1?. if the condition to deassert is true, then the interrupt source flag is cleared and nint is also deasserted. if the condition to deassert is false, then the interrupt source flag remains set, and the nint remains asserted. for example, setting the int7 bit in the interrupt mask register will enable the energyon interrupt. after a cable is plugged in, the energyon bit in the mode control/status register goes active and nint will be asserted low. to de-assert t he nint interrupt output, either clear the energyon bit in the mode control/status register by removing the cable and then writing a ?1? to the int7 bit in the interrupt mask register , or clear the int7 mask (bit 7 of the interrupt mask register ). note: the energyon bit in the mode control/status register is defaulted to a ?1? at the start of the signal acquisition process, therefore the int7 bit in the interrupt mask register will also read as a ?1? at power-up. if no signal is present, then both energyon and int7 will clear within a few milliseconds. table 3.3 alternative interrupt system management table mask interrupt source flag interrupt source event to assert nint condition to de-assert bit to clear nint 30.7 29.7 energyon 17.1 energyon rising 17.1 17.1 low 29.7 30.6 29.6 auto-negotiation complete 1.5 auto-negotiate complete rising 1.5 1.5 low 29.6 30.5 29.5 remote fault detected 1.4 remote fault rising 1.4 1.4 low 29.5 30.4 29.4 link down 1.2 link st atus falling 1.2 1.2 high 29.4 30.3 29.3 auto-negotiation lp acknowledge 5.14 acknowledge rising 5.14 5.14 low 29.3 30.2 29.2 parallel detection fault 6.4 parallel detection fault rising 6.4 6.4 low 29.2 30.1 29.1 auto-negotiation page received 6.1 page received rising 6.1 6.1 low 29.1
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 31 revision 1.4 (08-23-12) datasheet 3.7 configuration straps configuration straps allow various features of the device to be automatically configured to user defined values. configuration straps are latched upon power-on reset (por) and pin reset (nrst). configuration straps include internal resistors in order to prevent the signal from floating when unconnected. if a particular configur ation strap is connected to a load, an external pull-up or pull-down resistor should be used to augment the internal resi stor to ensure that it reaches the required voltage level prior to latching. the internal resistor can also be overridden by the addition of an external resistor. note: the system designer must guarantee that co nfiguration strap pins meet the timing requirements specified in section 5.5.3, "power-on nrst & configuration strap timing," on page 70 . if configuration strap pins are not at the correct voltage level prior to being latched, the device may capture incorrect strap values. note: when externally pulling configuration straps hi gh, the strap should be tied to vddio, except for regoff and nintsel which should be tied to vdd2a. 3.7.1 phyad[0] : phy address configuration the phyad0 bit is driven high or low to give each phy a unique address. this address is latched into an internal register at the end of a hardware reset (default = 0b). in a multi-phy application (such as a repeater), the controller is able to manage ea ch phy via the unique address. each phy checks each management data frame for a matching address in the relevant bits. when a match is recognized, the phy responds to that particular frame. the phy address is also used to seed the scrambler. in a multi-phy application, this ensures that the scramblers ar e out of synchronization and disperses the electromagnetic radiation ac ross the frequency spectrum. the device?s smi address may be configured using har dware configuration to either the value 0 or 1. the user can configure the phy address using softwa re configuration if an address greater than 1 is required. the phy address can be written (after smi communication at some address is established) using the phyad bits of the special modes register . the phyad0 hardware configuration strap is multiplexed with the rxer pin. 3.7.2 mode[2:0] : mode configuration the mode[2:0] configuration straps control the configuration of the 10/100 digital block. when the nrst pin is deasserted, the register bit va lues are loaded according to the mode[2:0] configuration straps. the 10/100 digital block is then configured by the register bit values. when a soft reset occurs via the soft reset bit of the basic control register , the configuration of the 10/100 digital block is controlled by the register bi t values and the mode[2:0] configuration straps have no affect. the device?s mode may be configured using the hardware configuration straps as summarized in table 3.4 . the user may configure the transceiv er mode by writing the smi registers.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 32 smsc LAN8720A/LAN8720Ai datasheet the mode[2:0] hardware configur ation pins are multiplexed with other signals as shown in ta b l e 3 . 5 . 3.7.3 regoff : internal +1.2v regul ator configuration the incorporation of flexpwr techno logy provides the ability to dis able the internal +1.2v regulator. when the regulator is dis abled, an external +1.2v must be supp lied to the vddcr pin. disabling the internal +1.2v regulator ma kes it possible to reduce total system power, since an external switching regulator with greater efficiency (v ersus the internal linear regulator) can be used to provide +1.2v to the transceiver circuitry. note: because the regoff configuration strap shares functi onality with the led1 pin, proper consideration must also be given to the led polarity. refer to section 3.8.1.1, "regoff and led1 polarity selection," on page 37 for additional information on the relation between regoff and the led1 polarity. table 3.4 mode[2:0] bus mode[2:0] mode definitions default register bit values register 0 register 4 [13,12,10,8] [8,7,6,5] 000 10base-t half duplex. auto-negotiation disabled. 0000 n/a 001 10base-t full duplex. auto-negotiation disabled. 0001 n/a 010 100base-tx half duplex. auto-negotiation disabled. crs is active during transmit & receive. 1000 n/a 011 100base-tx full duplex. auto-negotiation disabled. crs is active during receive. 1001 n/a 100 100base-tx half duplex is advertised. auto- negotiation enabled. crs is active during transmit & receive. 1100 0100 101 repeater mode. auto -negotiation enabled. 100base-tx half duplex is advertised. crs is active during receive. 1100 0100 110 power down mode. in this mode the transceiver will wake-up in power-down mode. the transceiver cannot be used when the mode[2:0] bits are set to this mode. to exit this mode, the mode bits in register 18.7:5(see section 4.2.9, "special modes register," on page 57 ) must be configured to some other value and a soft reset must be issued. n/a n/a 111 all capable. auto-negotiation enabled. x10x 1111 table 3.5 pin names for mode bits mode bit pin name mode[0] rxd0/mode0 mode[1] rxd1/mode1 mode[2] crs_dv/mode2
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 33 revision 1.4 (08-23-12) datasheet 3.7.3.1 disabling the internal +1.2v regulator to disable the +1.2v internal regulator, a pull-up strapping resistor should be connected from the regoff configuration strap to vdd2a. at power-on, after both vddio and vdd2a are within specification, the transc eiver will sample regoff to determine whether the internal regulator should turn on. if the pin is sampled at a voltage greater than v ih , then the internal regu lator is disabled and the system must supply +1.2v to the vddcr pin. t he vddio voltage must be at least 80% of the operating voltage level (1.44v when operating at 1.8v, 2.0v when operating at 2.5v, 2.64v when operating at 3.3v) before voltage is applied to vddcr. as described in section 3.7.3.2 , when regoff is left floating or connected to vss, the inte rnal regulator is enabled and the system is not required to supply +1.2v to the vddcr pin. 3.7.3.2 enabling the internal +1.2v regulator the +1.2v for vddcr is supplied by the on-chip regul ator unless the transceiver is configured for the regulator off mode using the regoff configuration strap as described in section 3.7.3.1 . by default, the internal +1.2v regulator is enabled when regoff is floating (due to the internal pull-down resistor). during power-on, if regoff is sampled below v il , then the internal +1.2v regulator will turn on and operate with power from the vdd2a pin. 3.7.4 nintsel : nint/refclko configuration the nintsel configuration strap is used to select between one of two available modes: ref_clk in mode (nint) and ref_clk out mode. the configured mode determines the function of the nint/refclko pin. the nintsel configuration strap is latched at por and on the rising edge of the nrst. by default, nintsel is configured for nint mode via the internal pull-up resistor. the rmii ref_clk is a continuous clock that provi des the timing reference for crs_dv, rxd[1:0], txen, txd[1:0] and rxer. the device uses ref_clk as the network clock such that no buffering is required on the transmit data path. however, on the receive data path, the receiver recovers the clock from the incoming data stream. the device us es elasticity buffering to accommodate for differences between the recovered clock and the local ref_clk. in ref_clk in mode, the 50mhz ref_clk is driven on the xtal1/clkin pin. this is the traditional system configuration when using rmii, and is described in section 3.7.4.1 . when configured for ref_clk out mode, the device gener ates the 50mhz rmii ref_clk and the nint interrupt is not available. ref_clk out mode allows a low-cost 25mhz crystal to be used as the reference for ref_clk. this configuratio n may result in reduced system cost and is described in section 3.7.4.2 . note: because the nintsel configuration strap shares func tionality with the led2 pin, proper consideration must also be given to the led polarity. refer to section 3.8.1.2, "nintsel and led2 polarity selection," on page 37 for additional information on the relation between nintsel and the led2 polarity. table 3.6 nintsel configuration strap value mode ref_clk description nintsel = 0 ref_clk out mode nint/refclko is the source of ref_clk. nintsel = 1 ref_clk in mode nint/refclko is an active low interrupt output. the ref_clk is sourced externally and must be driven on the xtal1/clkin pin.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 34 smsc LAN8720A/LAN8720Ai datasheet 3.7.4.1 ref_clk in mode in ref_clk in mode, the 50mhz ref_clk is driv en on the xtal1/clkin pi n. a 50mhz source for ref_clk must be available external to the device when using this mode. the clock is driven to both the mac and phy as shown in figure 3.7 . 3.7.4.2 ref_clk out mode to reduce bom cost, the device includes a feature to generate the rmii ref_clk signal from a low- cost, 25mhz fundamental crystal. this type of crystal is inexpensive in comparison to 3 rd overtone crystals that would normally be required for 50mhz . the mac must be capable of operating with an external clock to take advantage of this feature as shown in figure 3.8 . in order to optimize package size and cost, the refclko pin is multiplexe d with the nint pin. in ref_clk out mode, the nint functionality is disabled to accommodate usage of refclko as a 50mhz clock to the mac. note: the ref_clk out mode is not part of the rm ii specification. timing in this mode is not compliant with the rmii specification. to en sure proper system operati on, a timing analysis of the mac and lan8720 must be performed. figure 3.7 external 50mhz clock sources the ref_clk LAN8720A/LAN8720Ai 10/100 phy 24-qfn rmii txp txn mag rj45 rxp rxn xtal1/clkin xtal2 txd[1:0] 2 rxd[1:0] crs_dv 2 rmii led[2:1] 2 interface mdio mdc nint nrst txen mac accepts external 50mhz clock 50mhz reference clock all rmii signals are synchronous to the supplied clock ref_clk rxer
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 35 revision 1.4 (08-23-12) datasheet in some system architecture s, a 25mhz clock source is available. t he device can be us ed to generate the ref_clk to the mac as shown in figure 3.9 . it is important to note that in this specific example, only a 25mhz clock can be used (clock cannot be 50mhz). similar to the 25mhz crystal mode, the nint function is disabled. figure 3.8 sourcing ref_clk from a 25mhz crystal LAN8720A/LAN8720Ai 10/100 phy 24-qfn rmii txp txn mag rj45 rxp rxn 25mhz xtal1/clkin xtal2 led[2:1] 2 interface nrst txd[1:0] 2 rxd[1:0] crs_dv 2 rmii mdio mdc txen refclko mac capable of accepting 50mhz clock note: nint not available in this configuration rxer ref_clk
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 36 smsc LAN8720A/LAN8720Ai datasheet figure 3.9 sourcing ref_clk from external 25mhz source LAN8720A/LAN8720Ai 10/100 phy 24-qfn rmii txp txn mag rj45 rxp rxn xtal1/clkin xtal2 txd[1:0] 2 rxd[1:0] crs_dv 2 rmii led[2:1] 2 interface mdio mdc nrst txen refclko mac capable of accepting 50mhz clock note: nint is not available in this configuration rxer 25mhz clock ref_clk
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 37 revision 1.4 (08-23-12) datasheet 3.8 miscellaneous functions 3.8.1 leds two led signals are provided as a convenient means to determine the transceiver's mode of operation. all led signals are either active high or active low as described in section 3.8.1.2, "nintsel and led2 polarity selection" and section 3.8.1.1, "regoff and led1 polarity selection," on page 37 . the led1 output is driven active whenever the device detects a valid link, and blinks when crs is active (high) indicating activity. the led2 output is driven active when the operati ng speed is 100mbps. this led will go inactive when the operating speed is 10 mbps or during line isolation. note: when pulling the led1 and led2 pins hi gh, they must be tied to vdd2a, not vddio. 3.8.1.1 regoff and led1 polarity selection the regoff configuration strap is shared with the led1 pin. the led1 output will automatically change polarity based on the presenc e of an external pull-up resistor. if the led1 pin is pulled high to vdd2a by an external pull-up resistor to select a logical high for regoff , then the led1 output will be active low. if the led1 pin is pulled low by the in ternal pull-down resistor to select a logical low for regoff , the led1 output will then be an active high output. figure 3.10 details the led1 polarity for each regoff configuration. note: refer to section 3.7.3, "regoff: internal +1.2v regulator configuration," on page 32 for additional information on the regoff configuration strap. 3.8.1.2 nintsel and led2 polarity selection the nintsel configuration strap is shared with the le d2 pin. the led2 output will automatically change polarity based on the presence of an external pull-down resistor. if the led2 pin is pulled high to vdd2a to select a logical high for nintsel , then the led2 output will be active low. if the led2 figure 3.10 led1/regoff polarity configuration led1/regoff ~270 ohms regoff = 0 (regulator on) led output = active high ~270 ohms vdd2a regoff = 1 (regulator off) led output = active low led1/regoff 10k
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 38 smsc LAN8720A/LAN8720Ai datasheet pin is pulled low by an external pull-down resistor to select a logical low for nintsel , the led2 output will then be an active high output. figure 3.11 details the led2 polarity for each nintsel configuration. note: refer to section 3.7.4, "nintsel: nint/ref clko configuration," on page 33 for additional information on the nintsel configuration strap. 3.8.2 variable voltage i/o the device?s digital i/o pins are variable voltage, allowing them to take advantage of low power savings from shrinking technologies. these pins can operate from a low i/o voltage of +1.62v up to +3.6v. the applied i/o voltage must maintain its value with a tolerance of 10%. varying the voltage up or down after the transceiver has completed power-on rese t can cause errors in the transceiver operation. refer to chapter 5, "operational c haracteristics," on page 63 for additional information. note: input signals must not be driven high bef ore power is applied to the device. 3.8.3 power-down modes there are two device power-down modes: general power-down mode and energy detect power- down mode. these modes are descri bed in the following subsections. 3.8.3.1 general power-down this power-down mode is controlled via the power down bit of the basic control register . in this mode, the entire transceiver (exce pt the management interface) is powered-down and remains in this mode as long as the power down bit is ?1?. when the power down bit is cleared, the transceiver powers up and is automatically reset. 3.8.3.2 energy detect power-down this power-down mode is ac tivated by setting the edpwrdown bit of the mode control/status register . in this mode, when no energy is present on the line the transceiver is powered down (except for the management interface, the squelch circ uit, and the energyon logic). the energyon logic is used to detect the presence of valid energy from 100base-tx, 10base-t, or auto-negotiation signals. in this mode, when the energyon bit of the mode control/status register is low, the transceiver is powered-down and nothing is transmitted. when energy is received via link pulses or packets, the energyon bit goes high and the transceiver powers-up. the device automatically resets into the figure 3.11 led2/nintsel polarity configuration ~270 ohms nintsel = 0 led output = active high 10k ~270 ohms vdd2a nintsel = 1 led output = active low led2/nintsel led2/nintsel
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 39 revision 1.4 (08-23-12) datasheet state prior to power-down and asserts the nint inte rrupt if the energyon interrupt is enabled in the interrupt mask register . the first and possibly the second packe t to activate energyon may be lost. when the edpwrdown bit of the mode control/status register is low, energy detect power-down is disabled. 3.8.4 isolate mode the device data paths may be electrically isolat ed from the rmii interface by setting the isolate bit of the basic control register to ?1?. in isolation mode, the tran sceiver does not respond to the txd, txen and txer inputs, but does respond to management transactions. isolation provides a means for mult iple transceivers to be connected to the same rmii interface without contention. by default, the transceiver is not isolated (on power-up ( isolate =0). 3.8.5 resets the device provides two forms of reset: hardware and software. the device registers are reset by both hardware and software resets. select register bits, indicated as ?nasr? in the register definitions, are not cleared by a software reset. the regist ers are not reset by the power-down modes described in section 3.8.3 . note: for the first 16us after coming out of reset, the rmii interface will run at 2.5 mhz. after this time, it will switch to 25 mhz if auto-negotiation is enabled. 3.8.5.1 hardware reset a hardware reset is asserted by driving the nrst input pin low. when driven, nrst should be held low for the minimum time detailed in section 5.5.3, "power-on nrst & configuration strap timing," on page 70 to ensure a proper transceiver reset. du ring a hardware reset, an external clock must be supplied to the xtal1/clkin signal. note: a hardware reset (nrst assertion) is required following power-up. refer to section 5.5.3, "power-on nrst & configuration strap timing," on page 70 for additional information. 3.8.5.2 software reset a software reset is ac tivated by setting the soft reset bit of the basic control register to ?1?. all registers bits, except those indicated as ?nasr? in the register definitions, are cleared by a software reset. the soft reset bit is self-clearing. per the ieee 802.3u standard, clause 22 (22.2.4.1.1) the reset process will be completed within 0.5s from the setting of this bit. 3.8.6 carrier sense the carrier sense (crs) is output on the crs_dv pin. crs is a signal defined by the mii specification in the ieee 802.3u standard. the device asserts cr s based only on receive activity whenever the transceiver is either in repeater mode or full- duplex mode. otherwise the transceiver asserts crs based on either transmit or receive activity. the carrier sense logic uses the encoded, unscrambled data to determine carrier activity status. it activates carrier sense with the detection of 2 non-contiguous zeros within any 10 bit span. carrier sense terminates if a span of 10 consecutive ones is detected before a /j/k/ start-of stream delimiter pair. if an ssd pair is detected, carrier sense is asserted until either /t /r/ end?of-stream delimiter pair or a pair of idle symbols is detected. carrier is negated after the /t/ symbol or the first idle. if /t/ is not followed by /r/, then carrier is maintain ed. carrier is treated similarly for idle followed by some non-idle symbol.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 40 smsc LAN8720A/LAN8720Ai datasheet 3.8.7 link integrity test the device performs the link integrity test as out lined in the ieee 802.3u (clause 24-15) link monitor state diagram. the link status is multiplex ed with the 10mbps link status to form the link status bit in the basic status register and to drive the link led (led1). the dsp indicates a valid mlt-3 waveform present on the rxp and rxn signals as defined by the ansi x3.263 tp-pmd standard, to the link monitor state-machine, using the internal data_valid signal. when data_valid is asserted, the control logic moves into a link-ready state and waits for an enable from the auto-negotiation block. when re ceived, the link-up state is entered, and the transmit and receive logic blocks become active . should auto-negotiation be disabled, the link integrity logic moves immediately to the link-up state when the data_valid is asserted. to allow the line to stabilize, the link integrity logic will wait a minimum of 330 sec from the time data_valid is asserted until the link-ready stat e is entered. should the data_valid input be negated at any time, this logic will immediately negate the link signal and enter the link-down state. when the 10/100 digital bl ock is in 10base-t mode, the link status is derived from the 10base-t receiver logic. 3.8.8 loopback operation the device may be configured for near-end loopback and far loopback. these loopback modes are detailed in the following subsections. 3.8.8.1 near-end loopback near-end loopback mode sends the digital transmit data back out the receive data signals for testing purposes, as indicated by the blue arrows in figure 3.12 . the near-end loopback mode is enabled by setting the loopback bit of the basic control register to ?1?. a large percentage of the digital circuitry is operational in near-end loopback mode becau se data is routed through the pcs and pma layers into the pmd sublayer before it is looped back. the transmitters are powered down regardless of the state of txen. 3.8.8.2 far loopback far loopback is a special test mode for mdi (analog ) loopback as indicated by the blue arrows in figure 3.14 . the far loopback mode is enabled by setting the farloopback bit of the mode control/status register to ?1?. in this mode, data that is received from the link partner on the mdi is looped back out to the link partner. the digital interf ace signals on the local mac interface are isolated. figure 3.12 near-end loopback block diagram smsc ethernet transceiver 10/100 ethernet mac cat-5 xfmr digital rxd txd analog rx tx x x
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 41 revision 1.4 (08-23-12) datasheet 3.8.8.3 connector loopback the device maintains reliable transmission over ve ry short cables, and can be tested in a connector loopback as shown in figure 3.14 . an rj45 loopback cable can be used to route the transmit signals an the output of the transformer back to the receiver inputs, and this loopback will work at both 10 and 100. 3.9 application diagrams this section provides typical applic ation diagrams for the following: ? simplified system level application diagram ? power supply diagram (1.2v supplied by internal regulator) ? power supply diagram (1.2v supplied by external source) ? twisted-pair interface diagram (single power supply) ? twisted-pair interface diagram (dual power supplies) figure 3.13 far loopback block diagram figure 3.14 connector loopback block diagram far-end system smsc ethernet transceiver 10/100 ethernet mac cat-5 xfmr digital rxd txd analog rx tx link partner x x smsc ethernet transceiver 10/100 ethernet mac xfmr digital rxd txd analog rx tx 1 2 3 4 5 6 7 8 rj45 loopback cable. created by connecting pin 1 to pin 3 and connecting pin 2 to pin 6.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 42 smsc LAN8720A/LAN8720Ai datasheet 3.9.1 simplified system l evel application diagram figure 3.15 simplified system level application diagram LAN8720A/LAN8720Ai 10/100 phy 24-qfn rmii txp txn mag rj45 rxp rxn 25mhz xtal1/clkin xtal2 txd[1:0] 2 rxd[1:0] rxer 2 rmii led[2:1] 2 interface mdio mdc nint nrst txen
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 43 revision 1.4 (08-23-12) datasheet 3.9.2 power supply diagram (1.2v supplied by internal regulator) figure 3.16 power supply diagram (1 .2v supplied by internal regulator) LAN8720A/LAN8720Ai 24-qfn rbias vss 12.1k vdd2a c bypass c bypass vdd1a vddio c bypass c f vdddio supply 1.8 - 3.3v power supply 3.3v vddcr led1/ regoff ~270 ohm core logic internal regulator ch.2 3.3v circuitry in out ch.1 3.3v circuitry 470 pf 1 uf
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 44 smsc LAN8720A/LAN8720Ai datasheet 3.9.3 power supply diagram (1.2v supplied by external source) figure 3.17 power supply diagram (1 .2v supplied by external source) LAN8720A/LAN8720Ai 24-qfn rbias vss 12.1k vdd2a c bypass c bypass vdd1a vddio c bypass c f vdddio supply 1.8 - 3.3v power supply 3.3v vddcr led1/ regoff core logic internal regulator (disabled) ch.2 3.3v circuitry in out ch.1 3.3v circuitry vddcr supply 1.2v ~270 ohm 10k 470 pf 1 uf
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 45 revision 1.4 (08-23-12) datasheet 3.9.4 twisted-pair interface di agram (single power supply) figure 3.18 twisted-pair interface diagram (single power supply) magnetics LAN8720A/LAN8720Ai 24-qfn vdd2a c bypass txp txn power supply 3.3v 1 2 3 4 5 6 7 8 1000 pf 3 kv rj45 75 75 rxp rxn c bypass vdd1a c bypass 49.9 ohm resistors ferrite bead
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 46 smsc LAN8720A/LAN8720Ai datasheet 3.9.5 twisted-pair interface di agram (dual power supplies) figure 3.19 twisted-pair interface diagram (dual power supplies) magnetics LAN8720A/LAN8720Ai 24-qfn vdd2a c bypass txp txn power supply 3.3v 1 2 3 4 5 6 7 8 1000 pf 3 kv rj45 75 75 rxp rxn c bypass vdd1a c bypass 49.9 ohm resistors power supply 2.5v - 3.3v
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 47 revision 1.4 (08-23-12) datasheet chapter 4 register descriptions this chapter describes the various control and status registers (csr?s). all registers follow the ieee 802.3 (clause 22.2.4) management register set. all functionality and bit definitions comply with these standards. the ieee 802.3 specified register index (in decimal) is included with each register definition, allowing for addressing of these registers via the serial management interface (smi) protocol. 4.1 register nomenclature table 4.1 describes the register bit attribute notation used throughout this document. many of these register bit notations can be co mbined. some examples of this are shown below: ? r/w: can be written. will return current setting on a read. ? r/wac: will return current setting on a read. writing anything clears the bit. table 4.1 register bit types register bit type notation register bit description r read: a register or bit with this attribute can be read. w read: a register or bit with this attribute can be written. ro read only: read only. writes have no effect. wo write only: if a register or bit is write-only, reads will return unspecified data. wc write one to clear: writing a one clears the value. writing a zero has no effect wac write anything to clear: writing anything clears the value. rc read to clear: contents is cleared after the read. writes have no effect. ll latch low: clear on read of register. lh latch high: clear on read of register. sc self-clearing: contents are self-cleared after the being set. writes of zero have no effect. contents can be read. ss self-setting: contents are self-setting after being cleared. writes of one have no effect. contents can be read. ro/lh read only, latch high: bits with this attribute will stay high until the bi t is read. after it is read, the bit will either remain high if the high condition remains, or will go low if the high condition has been removed. if the bit has not been read, the bit will remain high regardless of a change to the high condition. this mode is used in some ethernet phy registers. nasr not affected by software reset. the state of nasr bits do not change on assertion of a software reset. reserved reserved field: reserved fields must be written with zeros to ensure future compatibility. the value of reserved bits is not guaranteed on a read.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 48 smsc LAN8720A/LAN8720Ai datasheet 4.2 control and status registers table 4.2 provides a list of supported registers. regist er details, including bit definitions, are provided in the proceeding subsections. table 4.2 smi register map register index (decimal) register name group 0 basic control register basic 1 basic status register basic 2 phy identifier 1 extended 3 phy identifier 2 extended 4 auto-negotiation advertisement register extended 5 auto-negotiation link partner ability register extended 6 auto-negotiation expansion register extended 17 mode control/status register vendor-specific 18 special modes vendor-specific 26 symbol error counter register vendor-specific 27 control / status indication register vendor-specific 29 interrupt source register vendor-specific 30 interrupt mask register vendor-specific 31 phy special control/status register vendor-specific
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 49 revision 1.4 (08-23-12) datasheet 4.2.1 basic control register note 4.1 the default value of this bit is determined by the mode[2:0] configuration straps. refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional information. index (in decimal): 0 size: 16 bits bits description type default 15 soft reset 1 = software reset. bit is self-clearing. when setting this bit do not set other bits in this register. the configuration (as described in section 3.7.2, "mode[2:0]: mode configuration," on page 31 ) is set from the register bit values, and not from the mode pins. r/w sc 0b 14 loopback 0 = normal operation 1 = loopback mode r/w 0b 13 speed select 0 = 10mbps 1 = 100mbps note: ignored if auto-negotiation is enabled (0.12 = 1). r/w note 4.1 12 auto-negotiation enable 0 = disable auto-negotiate process 1 = enable auto-negotiate process (overrides 0.13 and 0.8) r/w note 4.1 11 power down 0 = normal operation 1 = general power down mode note: the auto-negotiation enable must be cleared before setting the power down. r/w 0b 10 isolate 0 = normal operation 1 = electrical isolation of phy from the rmii r/w 0b 9 restart auto-negotiate 0 = normal operation 1 = restart auto-negotiate process note: bit is self-clearing. r/w sc 0b 8 duplex mode 0 = half duplex 1 = full duplex note: ignored if auto-negotiation is enabled (0.12 = 1). r/w note 4.1 7:0 reserved ro -
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 50 smsc LAN8720A/LAN8720Ai datasheet 4.2.2 basic status register index (in decimal): 1 size: 16 bits bits description type default 15 100base-t4 0 = no t4 ability 1 = t4 able ro 0b 14 100base-tx full duplex 0 = no tx full duplex ability 1 = tx with full duplex ro 1b 13 100base-tx half duplex 0 = no tx half duplex ability 1 = tx with half duplex ro 1b 12 10base-t full duplex 0 = no 10mbps with full duplex ability 1 = 10mbps with full duplex ro 1b 11 10base-t half duplex 0 = no 10mbps with half duplex ability 1 = 10mbps with half duplex ro 1b 10 100base-t2 full duplex 0 = phy not able to perform full duplex 100base-t2 1 = phy able to perform full duplex 100base-t2 ro 0b 9 100base-t2 half duplex 0 = phy not able to perform half duplex 100base-t2 1 = phy able to perform half duplex 100base-t2 ro 0b 8 extended status 0 = no extended status information in register 15 1 = extended status information in register 15 ro 0b 7:6 reserved ro - 5 auto-negotiate complete 0 = auto-negotiate process not completed 1 = auto-negotiate process completed ro 0b 4 remote fault 1 = remote fault condition detected 0 = no remote fault ro/lh 0b 3 auto-negotiate ability 0 = unable to perform auto-negotiation function 1 = able to perform auto-negotiation function ro 1b 2 link status 0 = link is down 1 = link is up ro/ll 0b 1 jabber detect 0 = no jabber condition detected 1 = jabber condition detected ro/lh 0b 0 extended capabilities 0 = does not support extended capabilities registers 1 = supports extended capabilities registers ro 1b
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 51 revision 1.4 (08-23-12) datasheet 4.2.3 phy identifier 1 register index (in decimal): 2 size: 16 bits bits description type default 15:0 phy id number assigned to the 3rd through 18th bits of the organizationally unique identifier (oui), respectively. r/w 0007h
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 52 smsc LAN8720A/LAN8720Ai datasheet 4.2.4 phy identifier 2 register note 4.2 the default value of this field will vary dependant on the silicon revision number. index (in decimal): 3 size: 16 bits bits description type default 15:10 phy id number assigned to the 19th through 24th bits of the oui. r/w 110000b 9:4 model number six-bit manufacturer?s model number. r/w 001111b 3:0 revision number four-bit manufacturer?s revision number. r/w note 4.2
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 53 revision 1.4 (08-23-12) datasheet 4.2.5 auto negotiation advertisement register note 4.3 the default value of this bit is determined by the mode[2:0] configuration straps. refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional information. index (in decimal): 4 size: 16 bits bits description type default 15:14 reserved ro - 13 remote fault 0 = no remote fault 1 = remote fault detected r/w 0b 12 reserved ro - 11:10 pause operation 00 = no pause 01 = symmetric pause 10 = asymmetric pause toward link partner 11 = advertise support for both symmetric pause and asymmetric pause toward local device note: when both symmetric pause and asymmetric pause are set, the device will only be configured to, at most, one of the two settings upon auto-negotiation completion. r/w 00b 9 reserved ro - 8 100base-tx full duplex 0 = no tx full duplex ability 1 = tx with full duplex r/w note 4.3 7 100base-tx 0 = no tx ability 1 = tx able r/w 1b 6 10base-t full duplex 0 = no 10mbps with full duplex ability 1 = 10mbps with full duplex r/w note 4.3 5 10base-t 0 = no 10mbps ability 1 = 10mbps able r/w note 4.3 4:0 selector field 00001 = i eee 802.3 r/w 00001b
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 54 smsc LAN8720A/LAN8720Ai datasheet 4.2.6 auto negotiation link partner ability register index (in decimal): 5 size: 16 bits bits description type default 15 next page 0 = no next page ability 1 = next page capable note: this device does not support next page ability. ro 0b 14 acknowledge 0 = link code word not yet received 1 = link code word received from partner ro 0b 13 remote fault 0 = no remote fault 1 = remote fault detected ro 0b 12:11 reserved ro - 10 pause operation 0 = no pause supported by partner station 1 = pause supported by partner station ro 0b 9 100base-t4 0 = no t4 ability 1 = t4 able note: this device does not support t4 ability. ro 0b 8 100base-tx full duplex 0 = no tx full duplex ability 1 = tx with full duplex ro 0b 7 100base-tx 0 = no tx ability 1 = tx able ro 0b 6 10base-t full duplex 0 = no 10mbps with full duplex ability 1 = 10mbps with full duplex ro 0b 5 10base-t 0 = no 10mbps ability 1 = 10mbps able ro 0b 4:0 selector field 00001 = i eee 802.3 ro 00001b
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 55 revision 1.4 (08-23-12) datasheet 4.2.7 auto negotiation expansion register index (in decimal): 6 size: 16 bits bits description type default 15:5 reserved ro - 4 parallel detection fault 0 = no fault detected by parallel detection logic 1 = fault detected by parallel detection logic ro/lh 0b 3 link partner next page able 0 = link partner does not have next page ability 1 = link partner has next page ability ro 0b 2 next page able 0 = local device does not have next page ability 1 = local device has next page ability ro 0b 1 page received 0 = new page not yet received 1 = new page received ro/lh 0b 0 link partner auto-negotiation able 0 = link partner does not have auto-negotiation ability 1 = link partner has auto-negotiation ability ro 0b
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 56 smsc LAN8720A/LAN8720Ai datasheet 4.2.8 mode control/status register index (in decimal): 17 size: 16 bits bits description type default 15:14 reserved ro - 13 edpwrdown enable the energy detect power-down mode: 0 = energy detect power-down is disabled 1 = energy detect power-down is enabled r/w 0b 12:10 reserved ro - 9 farloopback enables far loopback mode (i.e., all the received packets are sent back simultaneously (in 100base-tx only)). this mode works even if the isolate bit (0.10) is set. 0 = far loopback mode is disabled 1 = far loopback mode is enabled refer to section 3.8.8.2, "far loopback," on page 40 for additional information. r/w 0b 8:7 reserved ro - 6 altint alternate interrupt mode: 0 = primary interrupt system enabled (default) 1 = alternate inte rrupt system enabled refer to section 3.6, "interrupt management," on page 29 for additional information. r/w 0b 5:2 reserved ro - 1 energyon indicates whether energy is detected. this bit transitions to ?0? if no valid energy is detected within 256ms. it is reset to ?1? by a hardware reset and is unaffected by a software reset. refer to section 3.8.3.2, "energy detect power-down," on page 38 for additional information. ro 1b 0 reserved r/w 0b
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 57 revision 1.4 (08-23-12) datasheet 4.2.9 special modes register note 4.4 the default value of this field is determined by the mode[2:0] configuration straps. refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional information. note 4.5 the default value of this field is determined by the phyad[0] configuration strap. refer to section 3.7.1, "phyad[0]: phy address configuration," on page 31 for additional information. index (in decimal): 18 size: 16 bits bits description type default 15 reserved ro - 14 reserved write as 1, ignore on read. r/w nasr 1b 13:8 reserved ro - 7:5 mode transceiver mode of operation. refer to section 3.7.2, "mode[2:0]: mode configuration," on page 31 for additional details. r/w nasr note 4.4 4:0 phyad phy address. the phy address is used for the smi address and for initialization of the cipher (scrambler) key. refer to section 3.7.1, "phyad[0]: phy address configuration," on page 31 for additional details. r/w nasr note 4.5
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 58 smsc LAN8720A/LAN8720Ai datasheet 4.2.10 symbol erro r counter register index (in decimal): 26 size: 16 bits bits description type default 15:0 sym_err_cnt the symbol error counter increments whenever an invalid code symbol is received (including idle symbols) in 100base-tx mode. the counter is incremented only once per packet, even when the received packet contains more than one symbol error. this counter increments up to 65,536 (2 16 ) and rolls over to 0 after reaching the maximum value. note: this register is cleared on reset, but is not cleared by reading the register. this register does no t increment in 10base-t mode. ro 0000h
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 59 revision 1.4 (08-23-12) datasheet 4.2.11 special control/stat us indications register index (in decimal): 27 size: 16 bits bits description type default 15 amdixctrl hp auto-mdix control: 0 = enable auto-mdix 1 = disable auto-mdix (use 27.13 to control channel) r/w 0b 14 reserved ro - 13 ch_select manual channel select: 0 = mdi (tx transmits, rx receives) 1 = mdix (tx receives, rx transmits) r/w 0b 12 reserved ro - 11 sqeoff disable the sqe test (heartbeat): 0 = sqe test is enabled 1 = sqe test is disabled r/w nasr 0b 10:5 reserved ro - 4 xpol polarity state of the 10base-t: 0 = normal polarity 1 = reversed polarity ro 0b 3:0 reserved ro -
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 60 smsc LAN8720A/LAN8720Ai datasheet 4.2.12 interrupt source flag register index (in decimal): 29 size: 16 bits bits description type default 15:8 reserved ro - 7 int7 0 = not source of interrupt 1 = energyon generated ro/lh 0b 6 int6 0 = not source of interrupt 1 = auto-negotiation complete ro/lh 0b 5 int5 0 = not source of interrupt 1 = remote fault detected ro/lh 0b 4 int4 0 = not source of interrupt 1 = link down (link status negated) ro/lh 0b 3 int3 0 = not source of interrupt 1 = auto-negotiation lp acknowledge ro/lh 0b 2 int2 0 = not source of interrupt 1 = parallel detection fault ro/lh 0b 1 int1 0 = not source of interrupt 1 = auto-negotiation page received ro/lh 0b 0 reserved ro 0b
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 61 revision 1.4 (08-23-12) datasheet 4.2.13 interrupt mask register index (in decimal): 30 size: 16 bits bits description type default 15:8 reserved ro - 7:1 mask bits 0 = interrupt source is masked 1 = interrupt source is enabled note: refer to section 4.2.12, "interrupt source flag register," on page 60 for details on the corresponding interrupt definitions. r/w 0000000b 0 reserved ro -
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 62 smsc LAN8720A/LAN8720Ai datasheet 4.2.14 phy special control/status register index (in decimal): 31 size: 16 bits bits description type default 15:13 reserved ro - 12 autodone auto-negotiation done indication: 0 = auto-negotiation is not done or disabled (or not active) 1 = auto-negotiation is done ro 0b 11:5 reserved - write as 00000 10b, ignore on read. r/w 0000010b 4:2 speed indication hcdspeed value: 001 = 10base-t half-duplex 101 = 10base-t full-duplex 010 = 100base-tx half-duplex 110 = 100base-tx full-duplex ro xxx 1:0 reserved ro -
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 63 revision 1.4 (08-23-12) datasheet chapter 5 operational characteristics 5.1 absolute maximum ratings* supply voltage (vddio, vdd1a, vdd2a) ( note 5.1 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5v to +3.6v digital core supply voltage (vddcr) ( note 5.1 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5v to +1.5v ethernet magnetics supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.5v to +3 .6v positive voltage on signal pins, with respect to ground ( note 5.2 ) . . . . . . . . . . . . . . . . . . . . . . . . . . +6v negative voltage on signal pins, with respect to ground ( note 5.3 ) . . . . . . . . . . . . . . . . . . . . . . . . -0.5v positive voltage on xtal1/clkin, with respect to ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +4.6v positive voltage on xtal2, with respect to ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2.5v ambient operating temperature in still air (t a ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . note 5.4 0 storage temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-55 o c to +150 o c junction to ambient ( ja ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59.8 o c/w junction to case ( jc ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12.6 o c/w lead temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . refer to jedec spec. j-std-020 hbm esd performance per jedec jesd22-a114. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .class 3a iec61000-4-2 contact discharge esd performance ( note 5.5 ) . . . . . . . . . . . . . . . . . . . . . . . . . .+/-8kv iec61000-4-2 air-gap discharge esd performance ( note 5.5 ) . . . . . . . . . . . . . . . . . . . . . . . . .+/-15kv latch-up performance per eia/jesd 78 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+/-150ma note 5.1 when powering this device from laboratory or system power supplies, it is important that the absolute maximum ratings not be exceeded or device failure can result. some power supplies exhibit voltage spikes on their outputs when ac power is switched on or off. in addition, voltage transients on the ac power line may appear on the dc output. if this possibility exists, it is suggeste d that a clamp circuit be used. note 5.2 this rating does not apply to the following pins: xtal1/clkin, xtal2, rbias. note 5.3 this rating does not apply to the following pins: rbias. note 5.4 0 o c to +85 o c for extended commercial version, -40 o c to +85 o c for industrial version. note 5.5 performed by independent 3rd party test facility. *stresses exceeding those listed in this section could cause permanent damage to the device. this is a stress rating only. exposure to absolute maximum rating conditions for extended periods may affect device reliability. functional operation of the device at any condition exceeding those indicated in section 5.2, "operating conditions**" , section 5.1, "absolute maximum ratings*" , or any other applicable section of this specification is not implied. note, device signals are not 5 volt tolerant unless specified otherwise.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 64 smsc LAN8720A/LAN8720Ai datasheet 5.2 operating conditions** supply voltage (vddio) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +1.62v t o +3.6v analog port supply voltage (vdd1a, vdd2a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +3.0v to +3.6v digital core supply voltage (vddcr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +1.14v to +1.26v ethernet magnetics supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2.25v to +3.6 v ambient operating temperature in still air (t a ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . note 5.4 **proper operation of the device is guaranteed only within the ranges specified in this section. after the device has completed power-up, vddio and the magnetics power supply must maintain their voltage level with +/-10%. varying the voltage greater than +/-10% after the device has completed power-up can cause errors in device operation. note: do not drive input signals without power supplied to the device. 5.3 power consumption this section details the device power measurement s taken over various operating conditions. unless otherwise noted, all measurements were taken with power supplies at nominal values (vddio, vdd1a, vdd2a = 3.3v, vddcr = 1.2v). see section 3.8.3, "power-down modes," on page 38 for a description of the power down modes. for more information on the ref_clk modes, see section 3.7.4, "nintsel: nint/refclko configuration," on page 33 . 5.3.1 ref_clk in mode table 5.1 device only current consumption and power dissipation (ref_clk in mode) power pin group vdda3.3 power pins(ma) vddcr power pin(ma) vddio power pin(ma) total current (ma) total power (mw) 100base-tx /w traffic max 28 21 0.6 49 159 typical 26 19 0.5 45 148 min 23 18 0.3 41 96 note 5.6 10base-t /w traffic max 9.7 13 0.6 24 77 typical 8.9 12 0.5 22 70 min 8.3 12 0.3 20 42 note 5.6 energy detect power down max 4.2 3.0 0.2 7.4 25 typical 4.1 1.9 0.2 6.2 21 min 3.9 1.9 0 5.8 16 note 5.6 general power down max 0.4 2.8 0.2 3.4 11.2 typical 0.3 1.8 0.2 2.3 7.6 min 0.3 1.7 0 2 3.0 note 5.6
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 65 revision 1.4 (08-23-12) datasheet note: the current at vddcr is either supplied by th e internal regulator from current entering at vdd2a, or from an external 1.2v supply when the internal regulator is disabled. note: current measurements do not include power applied to the magnetics or the optional external leds. the ethernet component current is typi cally 41ma in 100base-tx mode and 100ma in 10base-t mode, independent of the 2.5v or 3.3v supply rail of the transformer. note 5.6 calculated with full flexpwr features activa ted: vddio=1.8v & internal regulator disabled. 5.3.2 ref_clk out mode . note: the current at vddcr is either supplied by th e internal regulator from current entering at vdd2a, or from an external 1.2v supply when the internal regulator is disabled. note: current measurements do not include power applied to the magnetics or the optional external leds. the ethernet component current is typi cally 41ma in 100base-tx mode and 100ma in 10base-t mode, independent of the 2.5v or 3.3v supply rail of the transformer. note 5.7 calculated with full flexpwr features activa ted: vddio=1.8v & internal regulator disabled. table 5.2 device only current consumption and power dissipation (ref_clk out mode) power pin group vdda3.3 power pins(ma) vddcr power pin(ma) vddio power pin(ma) total current (ma) total power (mw) 100base-t /w traffic max 28 20 6.3 54 179 typical 26 19 5.8 50 164 min 22 15 2.9 39 93 note 5.7 10base-t /w traffic max 9.9 13 6.4 30 96 typical 8.8 12 5.6 26 85 min 7.1 10 3.0 20 41 note 5.7 energy detect power down max 4.5 2.7 0.3 7.5 25 typical 4.0 1.5 0.2 5.7 19 min 3.9 1.2 0 5.1 15 note 5.7 general power down max 0.4 2.5 0.2 3.1 10.2 typical 0.4 1.3 0.2 1.9 6.3 min 0.4 1.0 0 1.4 2.5 note 5.7
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 66 smsc LAN8720A/LAN8720Ai datasheet 5.4 dc specifications table 5.3 details the non-variable i/o buffer characteristics. these buffer types do not support variable voltage operation. ta b l e 5 . 4 details the variable voltage i/o buffer characteristics. typical values are provided for 1.8v, 2.5v, and 3.3v vddio cases. note 5.8 this specification applies to all inputs and tri-stated bi-directional pins. internal pull-down and pull-up resistors add +/- 50ua per-pin (typical). note 5.9 xtal1/clkin can optionally be driven from a 25mhz single-ended clock oscillator. table 5.3 non-variable i/o buffer characteristics parameter symbol min typ max units notes is type input buffer low input level high input level negative-going threshold positive-going threshold schmitt trigger hysteresis (v iht - v ilt ) input leakage (v in = vss or vddio) input capacitance v ili v ihi v ilt v iht v hys i ih c in -0.3 1.01 1.39 336 -10 1.19 1.59 399 3.6 1.39 1.79 459 10 2 v v v v mv ua pf schmitt trigger schmitt trigger note 5.8 o12 type buffers low output level high output level v ol v oh vdd2a - 0.4 0.4 v v i ol = 12ma i oh = -12ma iclk type buffer (xtal1 input) low input level high input level v ili v ihi -0.3 1.4 0.35 vdd2a + 0.4 v v note 5.9
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 67 revision 1.4 (08-23-12) datasheet note 5.10 this specification applies to all inputs and tri-stated bi-directional pins. internal pull-down and pull-up resistors add +/- 50ua per-pin (typical). note 5.11 measured at line side of transformer, line replaced by 100 (+/- 1%) resistor. note 5.12 offset from 16ns pulse width at 50% of pulse peak. note 5.13 measured differentially. table 5.4 variable i/o buffer characteristics parameter symbol min 1.8v typ 2.5v typ 3.3v typ max units notes vis type input buffer low input level high input level neg-going threshold pos-going threshold schmitt trigger hysteresis (v iht - v ilt ) input leakage (v in = vss or vddio) input capacitance v ili v ihi v ilt v iht v hys i ih c in -0.3 0.64 0.81 102 -10 0.83 0.99 158 1.15 1.29 136 1.41 1.65 138 3.6 1.76 1.90 288 10 2 v v v v mv ua pf schmitt trigger schmitt trigger note 5.10 vo8 type buffers low output level high output level v ol v oh vddio - 0.4 0.4 v v i ol = 8ma i oh = -8ma vod8 type buffer low output level v ol 0.4 v i ol = 8ma table 5.5 100base-tx transceiver characteristics parameter symbol min typ max units notes peak differential output voltage high v pph 950 - 1050 mvpk note 5.11 peak differential output voltage low v ppl -950 - -1050 mvpk note 5.11 signal amplitude symmetry v ss 98 - 102 % note 5.11 signal rise and fall time t rf 3.0 - 5.0 ns note 5.11 rise and fall symmetry t rfs --0.5ns note 5.11 duty cycle distortion d cd 35 50 65 % note 5.12 overshoot and undershoot v os --5% jitter 1.4 ns note 5.13
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 68 smsc LAN8720A/LAN8720Ai datasheet note 5.14 min/max voltages guaranteed as measured with 100 resistive load. 5.5 ac specifications this section details the various ac timing specifications of the device. note: the smi timing adheres to the ieee 802.3 specification. refer to the ieee 802.3 specification for additional timing information. note: the rmii timing adheres to the rmii consortium rmii specification r1.2. 5.5.1 equivalent test load output timing specifications assume a 25pf equivalent test load, unless otherwise noted, as illustrated in figure 5.1 below. table 5.6 10base-t transceiver characteristics parameter symbol min typ max units notes transmitter peak differential output voltage v out 2.2 2.5 2.8 v note 5.14 receiver differential squelch threshold v ds 300 420 585 mv figure 5.1 output equivalent test load 25 pf output
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 69 revision 1.4 (08-23-12) datasheet 5.5.2 power sequence timing this diagram illustrates the device power sequenc ing requirements. the vddio, vdd1a, vdd2a and magnetics power supplies can turn on in any order provided they all reach operational levels within the specified time period t pon . device power supplies can turn off in any order provided they all reach 0 volts within the specified time period p off . note: when the internal regulator is disabled, a power-up sequencing relationship exists between vddcr and the 3.3v power supply. for additional information refer to section 3.7.3, "regoff: internal +1.2v regulator configuration," on page 32 . figure 5.2 power sequence timing table 5.7 power sequence timing values symbol description min typ max units t pon power supply turn on time 50 ms t poff power supply turn off time 500 ms vddio magnetics power t pon t poff vdd1a, vdd2a
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 70 smsc LAN8720A/LAN8720Ai datasheet 5.5.3 power-on nrst & c onfiguration strap timing this diagram illustrates the nrst reset and conf iguration strap timing requirements in relation to power-on. a hardware reset (nrst assertion) is re quired following power-up. for proper operation, nrst must be asserted for no less than t rstia . the nrst pin can be asserted at any time, but must not be deasserted before t purstd after all external power supplies have reached 80% of their nominal operating levels. in order for valid configuration strap values to be read at power-up, the t css and t csh timing constraints must be followed. refer to section 3.8.5, "resets," on page 39 for additional information. note: nrst deassertion must be monotonic. note: device configuration straps are latched as a result of nrst assertion. refer to section 3.7, "configuration straps," on page 31 for details. configuration straps must only be pulled high or low and must not be driven as inputs. note 5.15 20 clock cycles for 25mhz, or 40 clock cycles for 50mhz. figure 5.3 power-on nrst & configuration strap timing table 5.8 power-on nrst & configuration strap timing values symbol description min typ max units t purstd external power supplies at 80% to nrst deassertion 25 ms t purstv external power supplies at 80% to nrst valid 0 ns t rstia nrst input assertion time 100 s t css configuration strap pins setup to nrst deassertion 200 ns t csh configuration strap pins hold after nrst deassertion 1 ns t otaa output tri-state after nrst assertion 50 ns t odad output drive after nrst deassertion 2 800 ( note 5.15 ) ns t css nrst configuration strap pins input t rstia t csh configuration strap pins output drive t odad all external power supplies t purstd 80% t purstv t otaa
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 71 revision 1.4 (08-23-12) datasheet 5.5.4 rmii interface timing 5.5.4.1 rmii timing (ref_clk out mode) the 50mhz ref_clk out timing applies to the case when nintsel is pulled-low. in this mode, a 25mhz crystal or clock oscillator must be i nput on the xtal1/clkin and xtal2 pins. for more information on ref_clk out mode, see section 3.7.4.2, "ref_clk out mode," on page 34 . note 5.16 timing was designed for system load between 10 pf and 25 pf. figure 5.4 rmii timing (ref_clk out mode) table 5.9 rmii timing values (ref_clk out mode) symbol description min max units notes t clkp refclko period 20 ns t clkh refclko high time t clkp *0.4 t clkp *0.6 ns t clkl refclko low time t clkp *0.4 t clkp *0.6 ns t oval rxd[1:0], rxer, crs_dv output valid from rising edge of refclko 5.0 ns note 5.16 t ohold rxd[1:0], rxer, crs_dv output hold from rising edge of refclko 1.4 ns note 5.16 t su txd[1:0], txen setup time to rising edge of refclko 7.0 ns note 5.16 t ihold txd[1:0], txen input hold time after rising edge of refclko 2.0 ns note 5.16 refclko rxd[1:0], rxer crs_dv t clkh t clkl t clkp t oval t ohold t oval t oval t ohold t su txd[1:0] txen t ihold t su t ihold t ihold t su t ihold
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 72 smsc LAN8720A/LAN8720Ai datasheet 5.5.4.2 rmii timing (ref_clk in mode) the 50mhz ref_clk in timing applies to the case when nintsel is floated or pulled-high. in this mode, a 50mhz clock must be input on the clkin pin. for more information on ref_clk in mode, see section 3.7.4.1, "ref_clk in mode," on page 34 . note 5.17 timing was designed for system load between 10 pf and 25 pf. figure 5.5 rmii timing (ref_clk in mode) table 5.10 rmii timing values (ref_clk in mode) symbol description min max units notes t clkp clkin period 20 ns t clkh clkin high time t clkp *0.35 t clkp *0.65 ns t clkl clkin low time t clkp *0.35 t clkp *0.65 ns t oval rxd[1:0], rxer, crs_dv output valid from rising edge of clkin 14.0 ns note 5.17 t ohold rxd[1:0], rxer, crs_dv output hold from rising edge of clkin 3.0 ns note 5.17 t su txd[1:0], txen setup time to rising edge of clkin 4.0 ns note 5.17 t ihold txd[1:0], txen input hold time after rising edge of clkin 1.5 ns note 5.17 clkin (ref_clk) rxd[1:0], rxer crs_dv t clkh t clkl t clkp t oval t ohold t oval t oval t ohold t su txd[1:0] txen t ihold t su t ihold t ihold t su t ihold
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 73 revision 1.4 (08-23-12) datasheet 5.5.4.3 rmii clkin requirements 5.5.5 smi timing this section specifies the smi timing of the device. please refer to section 3.5, "serial management interface (smi)," on page 28 for additional details. table 5.11 rmii clkin (ref_clk) timing values parameter min typ max units notes clkin frequency 50 mhz clkin frequency drift 50 ppm clkin duty cycle 40 60 % clkin jitter 150 psec p-p ? not rms figure 5.6 smi timing table 5.12 smi timing values symbol description min max units notes t clkp mdc period 400 ns t clkh mdc high time 160 (80%) ns t clkl mdc low time 160 (80%) ns t val mdio (read from phy) output valid from rising edge of mdc 300 ns t ohold mdio (read from phy) output hold from rising edge of mdc 0ns t su mdio (write to phy) setup time to rising edge of mdc 10 ns t ihold mdio (write to phy) inpu t hold time after rising edge of mdc 10 ns mdc mdio t clkh t clkl t clkp t ohold mdio t su t ihold (data-out) (data-in) t ohold t val
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 74 smsc LAN8720A/LAN8720Ai datasheet 5.6 clock circuit the device can accept either a 25mhz crystal or a 25mhz single-ended cloc k oscillator (50ppm) input. if the single-ended clock oscillator method is implemented, xtal2 should be left unconnected and xtal1/clkin should be driven with a nominal 0-3.3v clock signal. see ta b l e 5 . 1 3 for the recommended crystal specifications. note 5.18 the maximum allowable values for frequen cy tolerance and frequency stability are application dependant. since any particular application must meet the ieee 50 ppm total ppm budget, the combination of these two values must be approximately 45 ppm (allowing for aging). note 5.19 frequency deviation over time is also referred to as aging. note 5.20 the total deviation for the transmitter clock frequency is specified by ieee 802.3u as 100 ppm. note 5.21 0 o c for extended commercial version, -40 o c for industrial version. note 5.22 this number includes the pad, the bond wire and the lead frame. pcb capacitance is not included in this value. the xtal1/clkin pin, xtal2 pin and pcb capacitance values are required to accurately calculate the value of the two external load capacitors. the total load capacitance must be equivalent to what the crystal expects to see in the circuit so that the crystal oscillator will operate at 25.000 mhz. table 5.13 crystal specifications parameter symbol min nom max units notes crystal cut at, typ crystal oscillation mode fundamental mode crystal calibration mode parallel resonant mode frequency f fund - 25.000 - mhz frequency tolerance @ 25 o cf tol --50ppm note 5.18 frequency stability over temp f temp --50ppm note 5.18 frequency deviation over time f age - +/-3 to 5 - ppm note 5.19 total allowable ppm budget - - 50 ppm note 5.20 shunt capacitance c o -7 typ-pf load capacitance c l - 20 typ - pf drive level p w 300 - - uw equivalent series resistance r 1 --30ohm operating temperature range note 5.21 -+85 o c xtal1/clkin pin capacitance - 3 typ - pf note 5.22 xtal2 pin capacitance - 3 typ - pf note 5.22
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 75 revision 1.4 (08-23-12) datasheet chapter 6 package outline notes: 1. all dimensions are in mill imeters unless otherwise noted. 2. dimension ?b? applies to plated terminals and is m easured between 0.15 and 0.30 mm from the terminal tip. 3. the pin 1 identifier may vary, but is always located within the zone indicated. min nominal max remarks a 0.70 0.85 1.00 overall package height a1 0 0.02 0.05 standoff a2 - - 0.90 mold cap thickness d/e 3.90 4.00 4.10 x/y body size d1/e1 3.55 3.75 3.95 x/y mold cap size d2/e2 2.40 2.50 2.60 x/y exposed pad size l 0.30 0.40 0.50 terminal length b 0.18 0.25 0.30 terminal width k 0.25 - - terminal to exposed pad clearance e 0.50 bsc terminal pitch
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 76 smsc LAN8720A/LAN8720Ai datasheet
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 77 revision 1.4 (08-23-12) datasheet note: standard reel size is 4000 pieces per reel.
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet revision 1.4 (08-23-12) 78 smsc LAN8720A/LAN8720Ai datasheet chapter 7 datasheet revision history table 7.1 customer revision history revision level & date secti on/figure/entr y correction rev. 1.4 (08-23-12) section 4.2.2, "basic status register," on page 50 updated definitions of bits 10:8. section 4.2.11, "special control/status indications register," on page 59 updated bit 11 definition. rev. 1.3 (03-12-12) company disclaimer on page 2 removed company address and phone numbers. rev. 1.3 (04-20-11) table 5.9, ?rmii timing values (ref_clk out mode),? on page 71 updated t oval maximum value from 10.0ns to 5.0ns. table 2.7, ?power pins,? on page 14 updated vddcr pin note to include requirement of 1uf and 470pf decoupling capacitors in parallel to ground on the vddcr pin. figure 3.16 power supply diagram (1.2v supplied by internal regulator) on page 43 and figure 3.16 power supply diagram (1.2v supplied by internal regulator) on page 43 updated diagrams to include 1uf and 470pf decoupling capacitors on the vddcr pin. rev. 1.2 (11-10-10) section 5.5.4, "rmii interface timing," on page 71 updated diagrams and tables to include rxer. section 3.7.4.2, "ref_clk out mode," on page 34 added timing note in section 3.7.4.2, "ref_clk out mode" section 5.5.4, "rmii interface timing," on page 71 corrected signal names on rmii timing diagrams and tables. updated table 5.9 t oval , t ohold , t su , and t ihold with 10 ns, 1.4 ns, 7.0 ns, and 2.0 ns, respectively. table 5.8, ?power-on nrst & configuration strap timing values,? on page 70 updated t odad description: ?output drive after nrst deassertion? rev. 1.1 (04-09-10) section 5.1, "absolute maximum ratings*" modified ?hbm esd performance by adding ?per jedec jesd22-a114? and changed ?+/-5kv? to ?class 3a? section 5.3, "power consumption," on page 64 corrected typo in the current consumption table row title: ?100ba se-tx /w traffic? section 5.3, "power consumption," on page 64 corrected typo in note regarding ethernet component current: ?the ethernet component current is typically 41ma in 100base-tx mode and 100ma in 10base-t mode, independent of the 2.5v or 3.3v supply rail of the transformer.?
small footprint rmii 10/100 ethernet transceiver with hp auto-mdix support datasheet smsc LAN8720A/LAN8720Ai 79 revision 1.4 (08-23-12) datasheet table 5.3, ?non-variable i/o buffer characteristics,? on page 66 corrected o12 v oh minimum value to ?vdd2a - 0.4? corrected iclk v ili maximum value to ?0.35? corrected iclk v ihi maximum value to ?vdd2a + 0.4? section 5.2, "operating conditions**," on page 64 added note: ?do not drive input signals without power supplied to the device.? section 5.1, "absolute maximum ratings*," on page 63 corrected iec61000-4-2 contact discharge esd performance to +/-8kv. section 4.2.4, "phy identifier 2 register," on page 52 corrected model number default value to ?001111b?. section 3.8.8.2, "far loopback," on page 40 added far loopback description. section 4.2.8, "mode control/status register," on page 56 added farloopback (bit 9) description. rev. 1.0 (12-09-09) document reworked for clarity and consistency with other smsc documentation. rev. 1.0 (04-15-09) initial release table 7.1 customer revision history (continued) revision level & date secti on/figure/entr y correction

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