PM4341AT1XC
DATA SHEET
PMC-900602
ISSUE 7
T1 FRAMER/TRANSCEIVER
ANSI T1.403-1989, and TR-TSY-000191. Alarm detection and validation for
SLC®96 is handled the same as SF framing format.
The ALMI block declares the presence of YELLOW alarm when the YELLOW
pattern has been received for 425 ms (± 50 ms); the YELLOW alarm is removed
when the YELLOW pattern has been absent for 425 ms (± 50 ms).The presence
of RED alarm is declared when an out-of-frame condition has been present for
2.55 sec (± 40 ms); the RED alarm is removed when the out-of-frame condition
has been absent for 16.6 sec (± 500 ms). In T1DM framing format the RED alarm
declaration criteria can be selected to be either 400 ms (± 100 ms) or 2.55 sec
(±40 ms); removal of the RED alarm in T1DM can be selected to be either 100
ms (±50 ms) or 16.6 sec (± 500 ms).The presence of AIS alarm is declared
when an out-of-frame condition and all-ones in the PCM data stream have been
present for 1.5 sec (±100 ms); the AIS alarm is removed when the AIS condition
has been absent for 16.8 sec (±500 ms).
-3
CFA alarm detection algorithms operate in the presence of a random 10 bit
error rate.
The ALMI also indicates the presence or absence of the YELLOW, RED, and AIS
alarm signal conditions over 40 ms, 40ms, and 60 ms intervals, respectively,
allowing an external microprocessor to integrate the alarm conditions via
software with any user-specific algorithms. Alarm indication is provided through
internal register bits.
8.12 Elastic Store (ELST)
The Elastic Store function is provided by the ELST block.
The ELST synchronizes incoming PCM frames to the local backplane clock,
BRCLK. The frame data is buffered in a two frame circular data buffer. Input
data is written to the buffer using a write pointer and output data is read from the
buffer using a read pointer.
When the backplane timing is derived from the receive line data (i.e. the RCLKO
output is used), the elastic store can be bypassed to eliminate the 2 frame delay.
In this configuration the elastic store can be used to measure frequency
differences between the recovered line clock and another 1.544 MHz clock
applied to the BRCLK input. A typical example might be to measure the
difference in frequency between two received T1 streams (i.e. East-West
frequency difference) by monitoring the number of SLIP occurrences of one
direction with respect to the other.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
44
PMC [ PMC-SIERRA, INC ]
