Cirrus Logic EP93xx User Manual

Page 353

DS785UM1

9-51

1/10/100 Mbps Ethernet LAN Controller

EP93xx User’s Guide

FCF

Address:

0x8001_0048 - Read/Write

Chip Reset:

0x0000_0000

Soft Reset:

0x0000_0000

Definition:

Flow Control Format Register

Bit Descriptions:

MACCT:

MAC Control Type. The MAC Control Type field defines
the Ethernet type field for receive and transmit MAC
control frames. This is used in the processing of transmit
and receive pause frames, which are a special form of
MAC control frames. For a receive frame to be identified
as a pause frame, the following conditions must be met:

• The destination address must match one of first two individual addresses, with the

appropriate RxFlowControlEn bit set.

• The Ethernet type field must match MAC Control Type.

• The first two data bytes of the frame must equal 0x0001.

When a transmit pause command is processed, the MAC Control Type is inserted in the
transmit frame as the ethernet type field.

TPT:

Transmit Pause Time. When a transmit pause command is
processed, the Transmit Pause Time is inserted as the
actual time to pause.

The format of a transmit pause frame is:

1. Destination address = Individual address[6] (6 bytes)

2. Source address = Individual address[0] (6 bytes)

3. Type field = MAC Control Type (2bytes)

4. Opcode = 0x0001 (2bytes)

MACCT

TPT