Output (MDIO) Module User's Guide

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Architecture

Table 2. EMAC and MDIO Signals for GMII Interface (continued)

Signal Type Description

MCRS I Carrier sense (MCRS). The MCRS pin is asserted by the PHY when the network is not idle in either

transmit or receive. The pin is de-asserted when both transmit and receive are idle. This signal is not

necessarily synchronous to MTCLK nor MRCLK. This pin is used in half-duplex operation only.

MRCLK I Receive clock (MRCLK). The receive clock is a continuous clock that provides the timing reference

for receive operations. The MRXD, MRXDV, and MRXER signals are tied to this clock. The clock is

generated by the PHY and is 2.5 MHZ at 10 Mbps operation, 25 MHZ at 100 Mbps operation and

125 MHZ at 1000 Mbps operation.

MRXD[7-0] I Receive data (MRXD). The receive data pins are a collection of 8 data signals comprising 8 bits of

data. MRDX0 is the least-significant bit (LSB). The signals are synchronized by MRCLK and valid

only when MRXDV is asserted.

MRXDV I Receive data valid (MRXDV). The receive data valid signal indicates that the MRXD pins are

generating nibble data for use by the EMAC. It is driven synchronously to MRCLK.

MRXER I Receive error (MRXER). The receive error signal is asserted for one or more MRCLK periods to

indicate that an error was detected in the received frame. This is meaningful only during data

reception when MRXDV is active.

MDCLK O Management data clock (MDCLK). The MDIO data clock is sourced by the MDIO module on the

system. It is used to synchronize MDIO data access operations done on the MDIO pin. The

frequency of this clock is controlled by the CLKDIV bits in the MDIO control register (CONTROL).

MDIO I/O Management data input output (MDIO). The MDIO pin drives PHY management data into and out of

the PHY by way of an access frame consisting of start of frame, read/write indication, PHY address,

bit cycles, when the pin acts as an input for read operations.

18 Ethernet Media Access Controller (EMAC)/Management Data Input/Output (MDIO) SPRUEQ6 – December 2007

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