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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)
V15
V14
V7
V6
SYMBOL
POSITION NAME AND DESCRIPTION
V15
VCR1.7
V0
VCR2.0
8.2 CRC4 Error Counter
CRC4 Count Register 1 (CRCCR1) is the most significant word and CRCCR2 is the least significant
word of a 10–bit counter that records word errors in the Cyclic Redundancy Check 4 (CRC4). Since the
maximum CRC4 count in a one second period is 1000, this counter cannot saturate. The counter is
disabled during loss of sync at either the FAS or CRC4 level; it will continue to count if loss of
multiframe sync occurs at the CAS level.
CRCCR1: CRC4 COUNT REGISTER 1 (Address=02 Hex)
CRCCR2: CRC4 COUNT REGISTER 2 (Address=03 Hex)
(MSB)
(note 1)
(note 1)
CRC7
CRC6
SYMBOL
POSITION NAME AND DESCRIPTION
CRC9
CRCCR1.1
CRC0
CRCCR2.0
NOTE:
The upper six bits of CRCCR1 at address 02 are the most significant bits of the 12–bit FAS error counter.
8.3 E–Bit Counter
E–bit Count Register 1 (EBCR1) is the most significant word and EBCR2 is the least significant word of
a 10–bit counter that records Far End Block Errors (FEBE) as reported in the first bit of frames 13 and 15
on E1 lines running with CRC4 multiframe. These count registers will increment once each time the
received E–bit is set to zero. Since the maximum E–bit count in a one second period is 1000, this counter
cannot saturate. The counter is disabled during loss of sync at either the FAS or CRC4 level; it will
continue to count if loss of multiframe sync occurs at the CAS level.
V13
V12
V5
V4
MSB of the 16–bit code violation count
LSB of the 16–bit code violation count
(note 1)
(note 1)
CRC5
CRC4
MSB of the 10–Bit CRC4 error count
LSB of the 10–Bit CRC4 error count
V11
V10
V3
V2
(note 1)
(note 1)
CRC/3
CRC2
45 of 117
DS21354 & DS21554
(LSB)
V9
V8
V1
V0
(LSB)
CRC9
CRC8
CRC1
CRC0
VCR1
VCR2
CRCCR1
CRCCR2
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