Cirrus Logic EP93xx - Manual (Page 353)

DS785UM1 9-51
Copyright 2007 Cirrus Logic
1/10/100 Mbps Ethernet LAN Controller
EP93xx User’s Guide
9
9
9
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)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
MACCT
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
TPT