DS2154
6 ERROR COUNT REGISTERS
There are a set of four counters in the DS2154 that record bipolar or code violations, errors in the CRC4
SMF codewords, E bits as reported by the far end, and word errors in the FAS. Each of these four
counters is automatically updated on either 1-second boundaries (CCR2.7 = 0) or every 62.5ms (CCR2.7
= 1) as determined by the timer in Status Register 2 (SR2.4). Hence, these registers contain performance
data from either the previous second or the previous 62.5ms. The user can use the interrupt from the timer
to determine when to read these registers. The user has a full second (or 62.5ms) to read the counters
before the data is lost.
6.1 BPV or Code Violation Counter
Violation Count Register 1 (VCR1) is the most significant word and VCR2 is the least significant word of
a 16-bit counter that records either Bipolar Violations (BPVs) or Code Violations (CVs). If CCR2.6 = 0,
then the VCR counts bipolar violations. Bipolar violations are defined as consecutive marks of the same
polarity. In this mode, if the HDB3 mode is set for the receive side via CCR1.2, then HDB3 codewords
are not counted as BPVs. If CCR2.6 = 1, then the VCR 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 DS2154 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 will not rollover. The bit error rate on an E1 line would have to be
greater than 10**-2 before the VCR would saturate.
VCR1: UPPER BIPOLAR VIOLATION COUNT REGISTER 1
(Address = 00 Hex)
VCR2: LOWER BIPOLAR VIOLATION COUNT REGISTER 2
(Address = 01 Hex)
(MSB)
(LSB)
V15
V14
V6
V13
V5
V12
V4
V11
V3
V10
V2
V9
V1
V8
VCR1
VCR2
V7
V0
SYMBOL
POSITION
NAME AND DESCRIPTION
V15
VCR1.7
MSB of the 16-bit bipolar or code violation count .
V0
VCR2.0
LSB of the 16-bit bipolar or code violation count.
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ROCHESTER [ Rochester Electronics ]
