PM8611-BIAP PMC [PMC-Sierra, Inc], PM8611-BIAP Datasheet - Page 62

• Manufacturer Part Number: PM8611-BIAP
• Manufacturer: PMC [PMC-Sierra, Inc]

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-2010883, Issue 2
In SBI mode: Encoded over the SBI336S frame alignment is SBI336S multiframe alignment that
is every four SBI336S frames or 500 µS. When carrying DS0 traffic in synchronous mode,
signaling multiframe alignment is also necessary and is also encoded over SBI336S alignment.
Signaling multiframe alignment is every 24 frames for T1 links and every 16 frames for E1 links,
therefore signaling multiframe alignment covering both T1 and E1 multiframe alignment is every
48 SBI336S frames or 6 ms. Therefore C1FP characters are sent every four or every 48 frames.
In TelecomBus mode: Encoded over the serial link is the tributary multiframe alignment which is
every 4 frames or 500 µS. Multiframe alignment is required so that a downstream device can
extract the T1 or E1 data from the tributary. The multiframe information is preserved by only
sending out C1FP characters every four frames.
The frame alignment state machine establishes frame alignment over the link and is based on the
frame and not the multiframe alignments. When the frame alignment state machine is in the out-
of-frame-alignment state, it maintains the current alignment, while searching for a C1FP
character. When it finds the C1FP character the state machine transitions to the in-frame-
alignment state. While in the in-frame-alignment state the state machine monitors out-of-place
C1FP characters. Out-of-place C1FP characters are identified by maintaining a frame counter
based on the C1FP character. The counter is initialized by the C1FP character when in the out-of-
character-alignment state, and is unaffected in the in-character-alignment state. If 3 consecutive
C1FPs have been found that do not agree with the expected location as defined by the frame
counter, the state will change to out-of-frame-alignment state.
The frame alignment state machine is also sensitive to character alignment. When the character
alignment state machine is in the out-of-character-alignment state, the frame alignment state
machine is forced out-of-alignment, and is held in that state until the character alignment state
machine transitions to the in-character alignment state.
SBSLITE™ Telecom Standard Product Data Sheet
Preliminary
61