Bt8370/8375/8376
3.12 Transmitter Registers
Fully Integrated T1/E1 Framer and Line Interface
TLOFC–TLOFA
Transmit Loss of Frame Criteria—Determines the number of frame errors that the online
framer must detect before declaring a loss of frame alignment [TLOF; addr 048]. Refer to
TFRAME [addr 070] to find which frame bits are monitored during the selected framer mode.
T1/E1N TLOFC–A
Reframe Criteria
0
1
1
1
100
001
010
100
3 consecutive FAS errors
2 out of 4 frame bit errors
2 out of 5 frame bit errors
2 out of 6 frame bit errors
NOTE(S): All other TLOFC–A combinations are invalid.
TZCS[1:0]
Transmit Zero Code Suppression—Selects ZCS and Pulse Density Violation (PDV)
enforcement options for XTIP/XRING and TPOSO/TNEGO outputs. B8ZS and HDB3
replace transmitted sequences of eight or four 0s with a recoverable code. These are standard
T1 and E1 line code options, respectively (see Table 3-20).
Table 3-20. Transmit Zero Code Suppression
Zero Code Substitution
(Sent left to right)
TZCS
T1/E1N
T1DM
ZCS
PDV
00
01
X
0
1
1
1
X
X
X
X
X
AMI
HDB3
B8ZS
UMC
AMI
None
None
None
000V or B00V
000VB0VB
10011000
01
None
10
None
11
Enforced
on PDV errors
AMI
Alternate Mark Inversion. Bipolar line code forces successive 1s to alternate their output pulse polarity. Analog and
digital dual-rail outputs are always AMI encoded, although certain AMI codes are modified to include 0 suppression.
HDB3
B8ZS
PDV
Prior to transmission, four consecutive 0s are substituted by 000V or B00V code, where B is an AMI pulse, and V is a
bipolar violation. ZCS encoder selects the code that forces the BPV output polarity opposite that of the prior BPV.
Prior to transmission, eight consecutive 0s are substituted by 000VB0VB code, where B is an AMI encoded pulse, and
V is a bipolar violation.
Enforcer overwrites transmit 0s that would otherwise cause output data to fail to meet the minimum required pulse
density per ANSI T1.403 sliding window.
NOTE(S): The enforcer never overwrites a framing bit and is not applicable during E1 mode.
NOTE(S): Each PDV-enforced 1 causes a nonrecoverable, transmitted bit error.
UMC
Unassigned Mux Code. DS0 channels containing eight 0s are substituted with the 10011000 code, per Bellcore
TA-TSY-000278.
NOTE(S): The receiver's ZCS decoder cannot recover original data content from UMC encoded signal.
NOTE(S): PRBS, inband loopback, and YB2 alarm insertion occurs after PDV enforcement; therefore, output data might violate
minimum pulse density requirements while these functions are active.
3-72
Conexant
N8370DSE
CONEXANT [ CONEXANT SYSTEMS, INC ]
