Rainbow Electronics DS21458 - Manual (Page 89)

DS21455/DS21458 Quad T1/E1/J1 Transceivers
89 of 270
15.3 Frames Out Of Sync Count Register (FOSCR)
15.3.1 T1 Operation
The FOSCR is used to count the number of multiframes that the receive synchronizer is out of sync. This
number is useful in ESF applications needing to measure the parameters loss of frame count (LOFC) and
ESF error events as described in AT&T publication TR54016. When the FOSCR is operated in this
mode, it is not disabled during receive loss of synchronization (RLOS = 1) conditions. The FOSCR has
alternate operating mode whereby it will count either errors in the Ft framing pattern (in the D4 mode) or
errors in the FPS framing pattern (in the ESF mode). When the FOSCR is operated in this mode, it is
disabled during receive loss of synchronization (RLOS = 1) conditions. See
Table 15-4 for a detailed
description of what the FOSCR is capable of counting.
Table 15-4. T1 FRAMES OUT OF SYNC COUNTING ARRANGEMENTS
FRAMING MODE
(T1RCR1.3)
COUNT MOS OR F-BIT ERRORS
(ERCNT.1)
WHAT IS COUNTED IN THE
FOSCRs
D4 MOS Number of Multiframes Out of Sync
D4 F-Bit Errors in the Ft Pattern
ESF MOS Number of Multiframes Out of Sync
ESF F-Bit Errors in the FPS Pattern
15.3.2 E1 Operation
The FOSCR counts word errors in the frame alignment signal in time slot 0. This counter is disabled
when RLOS is high. FAS errors will not be counted when the framer is searching for FAS alignment
and/or synchronization at either the CAS or CRC-4 multiframe level. Since the maximum FAS word
error count in a one-second period is 4000, this counter cannot saturate.
The FOSCR1 (FOSCR1) is the most significant word and FOSCR2 is the least significant word of a 16-
bit counter that records frames out of sync.