PM7346 datasheet(85/419 Pages) PMC

85 / 419 page

PM7346 S/UNI-QJET

DATASHEET

PMC-960835

ISSUE 6

SATURN QUAD USER NETWORK INTERFACE FOR J2, E3, T3

PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA INC., AND ITS CUSTOMERS’ INTERNAL USE 64

Figure 9

- Framing Algorithm (CRC_REFR = 1)

Mark multifram e alignm ent

C onfirm F ram ing Pattern

in nex t m ultifra m e

S lip 1 b it

Fra m ing

Patte rn

M a tc he d

Else

Fail

C onfirm F ram ing Pattern

in nex t m ultifra m e

Pass

Declare in-fram e

Pass

C hec k C R C -5 Sequence

Pass

C hec k C R C -5 Sequenc e

Fail

Res et

O ut o f Fram e

Fail

Using this algorithm, the J2-FRMR will find frame in 10.22ms, 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 loss of frame

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 1, the J2-FRMR

PM7346 Datasheet(PDF) 85 Page - PMC-Sierra, Inc