DS21354/DS21554 3.3V/5V E1 Single-Chip Transceivers
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7. ERROR COUNT REGISTERS
The DS21354/DS21554 have a set of four counters 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 one-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 one-second 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. All four counters will saturate at their respective
maximum counts and they will not rollover.
7.1.
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 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 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 V13 V12 V11 V10 V9 V8 VCR1
V7 V6 V5 V4 V3 V2 V1 V0
VCR2
SYMBOL
POSITION
NAME AND DESCRIPTION
V15 VCR1.7
MSB of the 16-bit code violation count.
V0 VCR2.0
LSB of the 16-bit code violation count.
