Output (MDIO) Module User's Guide

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Ethernet Media Access Controller (EMAC) Registers

Table 68. MAC Control Register (MACCONTROL) Field Descriptions (continued)

Bit Field Value Description

5 GMIIEN GMII enable bit.

0 GMII RX and TX are held in reset.

1 GMII RX and TX are enabled for receive and transmit.

4 TXFLOWEN Transmit flow control enable bit. This bit determines if incoming pause frames are acted upon

in full-duplex mode. Incoming pause frames are not acted upon in half-duplex mode,

regardless of the TXFLOWEN bit setting. The RXMBPENABLE bits determine whether or not

received pause frames are transferred to memory.

0 Transmit flow control is disabled. Full-duplex mode: incoming pause frames are not acted

upon.

1 Transmit flow control is enabled. Full-duplex mode: incoming pause frames are acted upon.

3 RXBUFFERFLOWEN Receive buffer flow control enable bit.

0 Receive flow control is disabled. Half-duplex mode: no flow control generated collisions are

sent. Full-duplex mode: no outgoing pause frames are sent.

1 Receive flow control is enabled. Half-duplex mode: collisions are initiated when receive buffer

flow control is triggered. Full-duplex mode: outgoing pause frames are sent when receive flow

control is triggered.

2 Reserved 0 Reserved

1 LOOPBACK Loopback mode. The loopback mode forces internal full-duplex mode regardless of the

FULLDUPLEX bit setting. The loopback bit should be changed only when GMIIEN bit is

deasserted.

0 Loopback mode is disabled.

1 Loopback mode is enabled.

0 FULLDUPLEX Full-duplex mode. The gigabit mode (GIG = 1) forces full-duplex mode regardless of the

FULLDUPLEX bit setting

0 Half-duplex mode is enabled.

1 Full-duplex mode is enabled.

SPRUEQ6 – December 2007 Ethernet Media Access Controller (EMAC)/Management Data Input/Output (MDIO) 111

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