VIA Technologies, Inc.
Preliminary VT6508 Datasheet
-36-
24-25H
Congestion Window On
Value 1: the port is in congestion status.
Value 0: the port is not in congestion status.
This signal is from Queue Control.
CONGEST_ON
[9:0]
0
R/O
26-27H
XOFF Window
Value 1: the port is in XOFF window.
Value 0: the port is in XON window.
This signal is from TMAC.
XOFF_WINDOW
[9:0]
0
R/O
30H
spanning tree state for PORT 0
2’ b00 - blocking state
2’ b01 – listening state
2’ b10 - learning state
2’ b11 – forwarding state (default)
The default value of all STP states is “ forwarding
state” .
The forwarding operation in each Ethernet port is
controlled by its associated spanning tree state.
In blocking or listening state, the incoming
packets will not trigger any DMAC lookup
operation and SMAC learning operation.
In learning state, the incoming packets will not
trigger DMAC lookup operation, but the SMAC
learning operation will be triggered for CRC-OK
packets.
Only in forwarding state, an incoming packet will
trigger DMAC lookup operation while the first 24
bytes are received, and it will trigger the SMAC
learning operation while the whole packet is
received with good CRC.
For the 802.1d spanning tree algorithm, a
blocked port for loop avoidance should enter the
blocking state so that any incoming packets are
filtered without forward. A normal port that does
not cause any loop should be in the forwarding
state.
PORT0_STP_STATE [1:0]
3
R/W
31H
spanning tree state for PORT 1
PORT1_STP_STATE [1:0]
3
R/W
32H
spanning tree state for PORT 2
PORT2_STP_STATE [1:0]
3
R/W
33H
spanning tree state for PORT 3
PORT3_STP_STATE [1:0]
3
R/W
34H
spanning tree state for PORT 4
PORT4_STP_STATE [1:0]
3
R/W
35H
spanning tree state for PORT 5
PORT5_STP_STATE [1:0]
3
R/W
36H
spanning tree state for PORT 6
PORT6_STP_STATE [1:0]
3
R/W
37H
spanning tree state for PORT 7
PORT7_STP_STATE [1:0]
3
R/W
38H
spanning tree state for PORT 8
PORT8_STP_STATE [1:0]
3
R/W
0400H PHY control
00H
CPU command port ID
Normally, it is the working port ID for CPU direct
read/write. It also shows the working port ID for
auto-polling debugging mode.
CMD_PORTID
[3:0]
0
R/W
01H
CPU command PHY REG number
PHY_REG_ADDR
[4:0]
0
R/W
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