SBI Bus Serializer ASSP Telecom Standard Product Data Sheet
Released
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2000168, Issue 5
81
In SBI mode: Encoded over the SBI336S frame alignment is SBI336S multi-frame alignment
which is every four SBI336S frames or 500uS. When carrying DS0 traffic in synchronous
mode, signaling multi-frame alignment is also necessary and is also encoded over SBI336S
alignment. Signaling multi-frame alignment is every 24 frames for T1 links and every 16 frames
for E1 links, therefore signaling multi-frame alignment covering both T1 and E1 multi-frame
alignment is every 48 SBI336S frames or 6ms. Therefore C1FP characters are sent every four
or every 48 frames.
In Telecom Bus mode: Encoded over the serial link is the tributary multi-frame alignment
which is every 4 frames or 500uS. Multi-frame alignment is required so that a downstream
device can extract the T1 or E1 data from the tributary. The multi-frame 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 multi-frame 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.