Altera Corporation
2–101
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Single-Width General Rate Matching
In Basic single-width mode, the rate matcher supports up to ±300 PPM
differences between the upstream transmitter and the receiver. The rate
matcher looks for the skip ordered set, which is a /K28.5/ comma
followed by three programmable neutral disparity skip characters (for
example, /K28.0/). For general rate matching, you can customize the SOS
to support a variety of protocols, including custom protocols. The SOS
must contain a valid control code group (Kx.y), followed by any neutral
disparity skip code group (any Kx.y or Dx.y of neutral disparity, for
example, K28.0). The rate matcher deletes or inserts skip characters when
necessary to prevent the rate matching FIFO buffer from overflowing or
underflowing.
The rate matcher in single-width mode can delete any number of skip
characters as necessary in a cluster as long as there are skip characters to
delete. There are no restrictions regarding deleting more than one skip
character in a cluster of skip characters.
Figure 2–76
shows an example of
a single-width mode rate matcher deletion of two skip characters.
Although the skip characters are programmable, the /K28.0/ control
group is used for illustration purposes.
Figure 2–76. Single-Width Mode Deletion of Two Skip Characters
The rate matcher inserts skip characters as required for rate matching. For
a given skip ordered set, the rate matcher inserts skip characters so that
the total number of consecutive skip characters does not exceed five at the
output of the rate matching FIFO buffer.
Figure 2–77
shows an example
where a skip character insertion is made on the second set of skip ordered
sets because the first set has the maximum number of skip characters.
K28.5
K28.0
K28.0
K28.0
Dx.y
K28.5
K28.0
K28.0
datain
clock
K28.5
K28.0
Dx.y
K28.5
K28.0
K28.0
Dx.y
Dx.y
dataout
Two Skips Deleted
Содержание Stratix II GX
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