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AM79C874VC Scheda tecnica(PDF) 10 Page - Advanced Micro Devices |
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AM79C874VC Scheda tecnica(HTML) 10 Page - Advanced Micro Devices |
10 / 60 page 10 Am79C874 P R E L I M INARY PIN DESCRIPTIONS The following table describes terms used in the pin de- scriptions. Media Connections TX± Transmitter Outputs Analog Output The TX pins are the differential transmit output pair. The TX pins transmit 10BASE-T or MLT-3 signals de- pending on the state of the link of the port. RX± Receiver Input Analog Input The RX pins are the differential receive input pair. The RX pins can receive 10BASE-T or MLT-3 signals de- pending on the state of the link of the port. FXT± FX Transmit Analog Output These pins are not connected in 10/100BASE-TX mode. When FX_SEL (Pin 44) is pulled low, these pins be- come the ECL level transmit output for 100BASE-FX. TEST0/FXR- Test Output/FX Receive -Analog Output/Input When BURN_IN (Pin 7) is pulled high, this pin serves as a test mode output monitor pin. When FX_SEL (Pin 44) is pulled low, this pin becomes an ECL level negative receive input for 100BASE-FX. This pin can be left unconnected when the device is op- erating in 100BASE-TX or 10BASE-T mode. TEST1/FXR+ Test Output/FX Receive +Analog Output/Input When BURN_IN (Pin 7) is pulled high, this pin serves as a test mode output monitor pin. When FX_SEL (Pin 44) is pulled low, this pin becomes an ECL level positive receive input for 100BASE-FX. This pin can be left unconnected when the device is op- erating in 100BASE-TX or 10BASE-T mode. TEST3/SDI+ FX Transceiver Signal Detect Analog Output/Input When BURN_IN (Pin 7) is pulled high, this pin serves as a test mode output monitor pin. This pin is not connected in 10/100BASE-TX mode. When FX_SEL (Pin 44) is pulled low, this pin becomes the Signal Detect input from the Fiber-Optic trans- ceiver. When the signal quality is good, the SDI+ pin should be driven high. MII/7-Wire (GPSI) Signals RXD[3:0] MII Receive Data Output, High Impedance The data is synchronous with RX_CLK when RX_DV is active. When the 7-wire 10BASE-T interface operation is enabled (GPIO[0]= HIGH), RXD[0] will serve as the 10 MHz serial data output. RX_DV Receive Data Valid Output, High Impedance RX_DV is asserted when the NetPHY-1LP device is presenting recovered nibbles on RXD[3:0]. This in- cludes the preamble through the last nibble of the data stream on RXD[3:0]. In 100BASE-X mode, the /J/K/ is considered part of the preamble; thus RX_DV is as- serted when /J/K/ is detected. In 10BASE-T mode, RX_DV is asser ted (and da ta is p resented o n RXD[3:0]) when the device detects valid preamble bits. RX_DV is synchronized to RX_CLK. RX_CLK/10RXCLK Receive Clock Output, High Impedance A continuous clock (which is active while LINK is estab- lished) provides the timing reference for RX_DV, RX_ER, and RXD[3:0] signals. It is 25 MHz in 100BASE-TX/FX and 2.5 MHz in 10BASE-T. To further reduce power consumption of the overall system, the device provides an optional mode enabled through MII Register 16, bit 0 in which RX_CLK is held inactive (low) when no data is received. If RX_CLK is needed when LINK is not established, the NetPHY-1LP must be placed into digital loopback or force the link via register 21, bits 13 or 14. When 7-wire 10BASE-T mode is enabled, this pin will provide a 10 MHz clock. RX_CLK is high impedance when the ISO pin is enabled RX_ER/RXD[4] Receive Error Output, High Impedance When RX_ER is active high, it indicates an error has been detected during frame reception. This pin becomes the highest-order bit of the receive 5- bit code group in PCS bypass (PCSBP=HIGH) mode. This output is ignored in 10BASE-T operation. Term Description Input Digital input to the PHY Analog Input Analog input to the PHY Output Digital output from the PHY Analog Output Analog output from the PHY High Impedance Tri-state capable output from the PHY Pull-Up PHY has internal pull-up resistor. NC=HIGH Pull-Down PHY has internal pull-down resistor. NC=LOW |
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