S/UNI®-JET Data Sheet
Released
When the CRC_REFR bit is set to logic zero, the J2-FRMR uses only the frame alignment
sequence to find frame, searching for three consecutive correct frame alignment sequences. The
frame find block searches for the entire 9-bit sequence (spread over two multiframes) at the same
time, greatly reducing the time required to find frame alignment. The framing process with CRC-
REFR cleared is illustrated in Figure 4.
Figure 4 Framing algorithm (CRC_REFR = 0)
Reset
Else
or
Slip 1 bit
Out of Frame
Framing
Pattern
Matched
Mark multiframe alignment
Fail
Fail
Confirm Framing Pattern
in next multiframe
Pass
Confirm Framing Pattern
in next multiframe
Pass
Declare in-frame
Using this algorithm, the J2-FRMR will on average find frame in 5.07 ms when starting the
4
-
search in the worst possible position, given a 10 error rate and no static mimic patterns.
When the CRC_REFR bit is set to logic one, in addition to requiring three consecutive correct
framing patterns, the J2-FRMR requires that the first two CRC-5 checks be correct, or a reframe
is initiated. To speed up the process, the CRC-5 and frame alignment checks are run concurrently,
as illustrated in Figure 5.
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990267, Issue 3
60
PMC [ PMC-SIERRA, INC ]
