PM7347 datasheet(61/341 Pages) PMC

61 / 341 page

S/UNI®-JET Data Sheet

Released

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

Document ID: PMC-1990267, Issue 3

Figure 5 Framing Algorithm (CRC_REFR = 1)

Mark multiframe alignment

Confirm Fram ing Pattern

in next m ultifram e

Slip 1 bit

Framing

Pattern

Matched

Else

Fail

Confirm Fram ing Pattern

in next m ultifram e

Pass

Declare in-frame

Pass

Check CRC-5 Sequence

Pass

Check CRC-5 Sequence

Fail

Reset

Out of Fram e

Fail

Using this algorithm, the J2-FRMR will find frame in 10.22 ms, on average when starting the

search in the worst possible position, given a 10-4 error rate and no static mimic patterns. The

algorithm will reject 99.90% of mimic patterns. Further protection against mimic patterns is

available by monitoring the rate of CRC-5 errors.

Once frame alignment is found, the block sets the LOF indication low, indicates a change of

frame alignment (if it occurred). The block declares LOF alignment if 7 consecutive FASs have

been received in error. In the presence of a random 10-3 bit error rate the frame loss criteria

provides a mean time to falsely lose frame alignment of 1.65 years. The Frame Find Block can be

forced to initiate a frame search at any time when the REFRAME bit in the J2-FRMR

configuration. Conversely, when the FLOCK bit is set to logic one, the J2-FRMR will never

declare LOF or search for a new frame alignment due to excess framing bit errors.

PM7347 датащи(PDF) 61 Page - PMC-Sierra, Inc