STANDARD PRODUCT
PM4328 TECT3
DATASHEET
PMC-2011596
ISSUE 1
HIGH DENSITY T1/E1 FRAMER
AND M13 MULTIPLEXER
9
FUNCTIONAL DESCRIPTION
9.1 T1 Framer (T1-FRMR)
The T1 framing function is provided by the T1-FRMR block. This block searches
for the framing bit position in the ingress stream. It works in conjunction with the
FRAM block to search for the framing bit pattern in the standard superframe
(SF), or extended superframe (ESF) framing formats. When searching for frame,
the FRMR simultaneously examines each of the 193 (SF) or each of the 772
(ESF) framing bit candidates. The FRAM block is addressed and controlled by
the FRMR while frame synchronization is acquired.
The time required to acquire frame alignment to an error-free ingress stream,
containing randomly distributed channel data (i.e. each bit in the channel data
has a 50% probability of being 1 or 0), is dependent upon the framing format.
For SF format, the T1-FRMR block will determine frame alignment within 4.4ms
99 times out of 100. For ESF format, the T1-FRMR will determine frame
alignment within 15 ms 99 times out of 100.
Once the T1-FRMR has found frame, the ingress data is continuously monitored
for framing bit errors, bit error events (a framing bit error in SF or a CRC-6 error
in ESF), and severely errored framing events. The T1-FRMR also detects out-of-
frame, based on a selectable ratio of framing bit errors.
The T1-FRMR can also be disabled to allow reception of unframed data.
9.2 E1 Framer (E1-FRMR)
The E1 framing function is provided by the E1-FRMR block. The E1-FRMR block
searches for basic frame alignment, CRC multiframe alignment, and channel
associated signaling (CAS) multiframe alignment in the incoming recovered PCM
stream.
Once the E1-FRMR has found basic (or FAS) frame alignment, the incoming
PCM data stream is continuously monitored for FAS/NFAS framing bit errors.
Framing bit errors are accumulated in the framing bit error counter contained in
the PMON block. Once the E1-FRMR has found CRC multiframe alignment, the
PCM data stream is continuously monitored for CRC multiframe alignment
pattern errors, and CRC-4 errors. CRC-4 errors are accumulated in the CRC
error counter of the PMON block. Once the E1-FRMR has found CAS
multiframe alignment, the PCM data is continuously monitored for CAS
multiframe alignment pattern errors. The E1-FRMR also detects and indicates
loss of basic frame, loss of CRC multiframe, and loss of CAS multiframe, based
PROPRIETARY AND CONFIDENTIAL
55
PMC [ PMC-SIERRA, INC ]
