Datasheet
DS2155
79 of 238
14.3 Frames Out-of-Sync Count Register (FOSCR)
14.3.1 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
an alternate operating mode whereby it counts 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. Table 14-D shows what the
FOSCR is capable of counting.
Table 14-D. T1 Frames Out-of-Sync Counting Arrangements
FRAMING MODE
(T1RCR1.3)
COUNT MOS OR
F-BIT ERRORS
(ERCNT.1)
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
14.3.2 E1 Operation
The FOSCR counts word errors in the FAS in time slot 0. This counter is disabled when RLOS is high.
FAS errors are not counted when the framer is searching for FAS alignment and/or synchronization at
either the CAS or CRC4 multiframe level. Since the maximum FAS word error count in a one-second
period is 4000, this counter cannot saturate.
The frames out-of-sync count register 1 (FOSCR1) is the most significant word and FOSCR2 is the least
significant word of a 16-bit counter that records frames out-of-sync.
Register Name:
FOSCR1
Register Description:
Frames Out-of-Sync Count Register 1
Register Address:
46h
Bit # 7 6 5 4 3 2 1 0
Name FOS15 FOS14 FOS13 FOS12 FOS11 FOS10 FOS9 FOS8
Default 0 0 0 0 0 0 0 0
Bits 0 to 7/Frames Out-of-Sync Counter Bits 8 to 15 (FOS8 to FOS15). FOS15 is the MSB of the 16-bit frames
out-of-sync count.
Register Name:
FOSCR2
Register Description:
Frames Out-of-Sync Count Register 2
Register Address:
47h
Bit # 7 6 5 4 3 2 1 0
Name FOS7 FOS6 FOS5 FOS4 FOS3 FOS2 FOS1 FOS0
Default 0 0 0 0 0 0 0 0
Bits 0 to 7/Frames Out-of-Sync Counter Bits 0 to 7 (FOS0 to FOS7). FOS0 is the LSB of the 16-bit frames out-
of-sync count.