Digi Rabbit 5000, User Manual

Page: 262 / 414

262 Rabbit 5000 Microprocessor User’s Manual
22.2 Dependencies
22.2.1 I/O Pins
The network port MII interface has 20 dedicated pins, which are listed in Table 22-1.
These pins can be used as general-purpose inputs and outputs if the network port is not
being used via NBDRR, NBDTR, and NBDMR.
22.2.2 Clocks
The network port requires a 25 MHz clock input for proper 10/100Base-T operation; this
clock is normally supplied separately to the receive and transmit portions of the peripheral
on the RX_CLK and TX_CLK pins. The management data clock on MDC is generated by
the Rabbit 5000 by dividing down the peripheral clock as selected in NBMCFR.
22.2.3 Other Registers
Table 22-1. Network Port MII Interface
Section Signal Direction Function
Transmit
TXD[3:0] Output Transmit data to PHY
TX_EN Output Transmit enable
TX_ER Output Transmit error
CRS Input Carrier sense
COL Input Collision detect
TX_CLK Input Transmit clock (25 MHz)
Receive
RXD[3:0] Input Receive data from PHY
RX_DV Input Receive data valid
RX_ER Input Receive data error
RX_CLK Input Receive clock (25 MHz)
Management
MDC Output Management data clock (varies)
MDI Input Management data input
MDO Output Management data output
MDOEN Output Management data output enable
Register Function
EDMR Enable 10/100 Ethernet functionality.