Altera Corporation
2–155
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Rate Matching
In PIPE mode, the rate matcher supports up to ±300 PPM (600 PPM total)
differences between the upstream transmitter and the receiver. The rate
matcher looks for skip ordered sets, which usually contain a /K28.5/
comma followed by three /K28.0/ skip characters. The rate matcher
deletes or inserts skip characters when necessary to prevent the rate
matching FIFO buffer from overflowing or underflowing.
The rate matcher can delete skip characters on only one skip character in
a consecutive cluster of skip characters.
Figure 2–116
shows an example
of a PIPE mode rate matcher deletion of two skip characters.
Figure 2–116. PIPE Mode With Two Deletions (One Deletion Per Cluster)
The rate matcher can insert skip characters one insertion per skip cluster.
There is no limit on the consecutive number of skip characters allowed
per skip cluster.
The Stratix II GX rate matcher in PIPE mode has FIFO buffer overflow
and underflow protection. In the event of a FIFO buffer overflow, the rate
matcher deletes any data after the overflow condition to prevent FIFO
pointer corruption until the rate matcher is not full. In an underflow
condition, the rate matcher inserts 9'h1FE (/K30.7/) until the FIFO buffer
is not empty. These measures ensure that the FIFO buffer can gracefully
exit the overflow/underflow condition without requiring a FIFO reset.
Power State
There are four supported power states in Stratix II GX devices: P0, P0s,
P1, and P2. P0 is the normal power state. P0s is a low recovery time power
state that is lower than P0. P1 is a lower power state than P0s and have
higher latency to come out of this state. P2 is the lowest power state
supported by this mode.
K28.5
K28.0
K28.0
K28.0
Dx.y
K28.5
K28.0
K28.0
datain
Skip Cluster
Skip Cluster
Skip Cluster
Skip Cluster
K28.5
K28.0
K28.0
Dx.y
K28.5
K28.0
Dx.y
Dx.y
dataout
Two Skips Deleted