lxt9781 Intel Corporation, lxt9781 Datasheet - Page 35

• Manufacturer Part Number: lxt9781
• Description: Fast Ethernet 10/100 Multi-port Transceiver With Rmii
• Manufacturer: Intel Corporation

2.7.2.2
Datasheet
1. The /I/ (Idle) code group is sent continuously between frames.
2. The /J/ and /K/ (SSD) code groups are always sent in pairs; /K/ follows /J/.
3. The /T/ and /R/ (ESD) code groups are always sent in pairs; /R/ follows /T/.
4. An /H/ (Error) code group is used to signal an error condition.
Code Type
CONTROL
Table 10. 4B/5B Coding (Continued)
INVALID
IDLE
PMA Sublayer
Link
In 100Mbps mode, the LXT97x1 establishes a link whenever the scrambler becomes locked and
remains locked for approximately 50 ms. Whenever the scrambler loses lock (<12 consecutive idle
symbols during a 2 ms window), the link will be taken down. This provides a very robust link,
essentially filtering out any small noise hits that may otherwise disrupt the link. Furthermore
100M idle patterns will not bring up a 10M link.
The LXT97x1 reports link failure via the RMII status bits (1.2, 17.10, and 19.4) and interrupt
functions. If auto-negotiate is enabled, link failure causes the LXT97x1 to re-negotiate.
Link Failure Override
The LXT97x1 will normally transmit 100 Mbps data packets or Idle symbols only if it detects the
link is up, and transmits only FLP bursts if the link is not up. Setting bit 16.14 = 1 overrides this
function, allowing the LXT97x1 to transmit data packets even when the link is down. This feature
is provided as a diagnostic tool. Note that auto-negotiation must be disabled to transmit data
packets in the absence of link. If auto-negotiation is enabled, the LXT97x1 will automatically
begin transmitting FLP bursts if the link goes down.
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4B Code
3 2 1 0
0 1 0 1
0 1 0 1
Fast Ethernet 10/100 Multi-Port Transceiver with RMII — LXT9761/9781
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Name
K
R
H
J
T
I
1
2
3
2
3
4
5B Code
4 3 2 1 0
1 1 0 0 0
1 0 0 0 1
0 1 1 0 1
0 0 1 1 1
0 0 1 0 0
0 0 0 0 0
0 0 0 0 1
0 0 0 1 0
0 0 0 1 1
0 0 1 0 1
0 0 1 1 0
0 1 0 0 0
0 1 1 0 0
1 0 0 0 0
1 1 0 0 1
1 1 1 11
Idle. Used as inter-stream fill code
Start-of-Stream Delimiter (SSD), part 1 of 2
Start-of-Stream Delimiter (SSD), part 2 of 2
End-of-Stream Delimiter (ESD), part 1 of 2
End-of-Stream Delimiter (ESD), part 2 of 2
Transmit Error. Used to force signaling errors
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Interpretation
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