PM7347 datasheet(60/341 Pages) PMC

60 / 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

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)

Mark multiframe alignment

Confirm Fram ing Pattern

in next m ultiframe

Slip 1 bit

Framing

Pattern

Matched

Reset

Out of Fram e

Else

Fail

Confirm Framing Pattern

in next m ultifram e

Fail

Pass

Declare in-frame

Pass

Using this algorithm, the J2-FRMR will on average find frame in 5.07 ms when starting the

search in the worst possible position, given a 10-4 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.

PM7347 Folha de dados(PDF) 60 Page - PMC-Sierra, Inc