Altera SerialLite II Protocol User Manual
Page 67
Altera Corporation
67
SerialLite II Protocol Reference Manual
SerialLite II Specification
6.
The near receiver must receive the ACK link management packets in
the same sequence that the segments are sent. The expected ID is
that of the oldest unacknowledged segment ID.
7.
A timeout must be implemented for the expected segment awaiting
acknowledgement. The timeout must force a resend if no
acknowledgment is received by the expiration of the timeout.
The following rules describe how segments are acknowledged by the far
receiver:
1.
When the far receiver gets a valid segment with the expected ID, it
acknowledges the segment with an ACK, advances the expected ID,
and stores the segment.
2.
When the far receiver gets a valid segment with an ID that it has
already received within the last eight segments, it acknowledges the
segment with an ACK, does not advance the expected ID, and
discards the segment. The received segment is simply dropped
without error.
3.
When the far receiver gets a valid segment with an ID that it
received prior to the last eight segments, it acknowledges the
segment with a NACK, does not advance the expected ID, and
discards the segment. The segment is considered to be received in
error.
4.
When the far receiver gets an invalid segment, it acknowledges the
segment with a NACK, does not advance the expected ID, and
discards the segment. An invalid segment is one with an invalid
8B/10B code, a disparity error, a CRC error, and so on.
5.
When the far receiver cannot fully enqueue a valid segment, it
acknowledges the segment with a NACK, does not advance the
expected ID, and discards the segment.
The following rules describe how the near receiver processes the ACK
and NACK link management segments that it receives:
1.
When the near receiver gets a valid ACK with the expected ID, it
clears the flag associated with that ID/buffer, and advances the
expected ID to the next segment ID in the sequence.
2.
When the near receiver gets a valid ACK with an ID that it has
already received within the last eight segments, it does nothing. The
link management segment is simply ignored.