Datasheet

DS2155
76 of 238
14.1 Line-Code Violation Count Register (LCVCR)
14.1.1 T1 Operation
T1 code violations are defined as bipolar violations (BPVs) or excessive 0s. If the B8ZS mode is set for
the receive side, then B8ZS codewords are not counted. This counter is always enabled; it is not disabled
during receive loss-of-synchronization (RLOS = 1) conditions. Table 14-A shows what the LCVCRs
count.
Table 14-A. T1 Line Code Violation Counting Options
COUNT EXCESSIVE
ZEROS?
(ERCNT.0)
B8ZS ENABLED?
(T1RCR2.5)
COUNTED IN THE LCVCRs
No No BPVs
Yes No BPVs + 16 consecutive 0s
No Yes BPVs (B8ZS codewords not counted)
Yes Yes BPVs + 8 consecutive 0s
14.1.2 E1 Operation
Either bipolar violations or code violations can be counted. Bipolar violations are defined as consecutive
marks of the same polarity. In this mode, if the HDB3 mode is set for the receive side, then HDB3
codewords are not counted as BPVs. If ERCNT.3 is set, then the LVC counts code violations as defined
in ITU O.161. Code violations are defined as consecutive bipolar violations of the same polarity. In most
applications, the framer should be programmed to count BPVs when receiving AMI code and to count
CVs when receiving HDB3 code. This counter increments at all times and is not disabled by loss-of-sync
conditions. The counter saturates at 65,535 and does not roll over. The bit-error rate on an E1 line would
have to be greater than 10
-2
before the VCR would saturate (Table 14-B).
Table 14-B. E1 Line-Code Violation Counting Options
E1 CODE VIOLATION SELECT
(ERCNT.3)
COUNTED IN THE LCVCRs
0 BPVs
1 CVs