2.0 Circuit Description
2.8 Transmitter
Bt8370/8375/8376
Fully Integrated T1/E1 Framer and Line Interface
The HDB3 line code replaces 4 consecutive 0s by 000V or B00V code, where
B is an AMI pulse and V is a bipolar violation (see Figure 2-32). ZCS encoder
selects the code that forces the BPV output polarity opposite to the prior BPV.
Figure 2-32. Zero Code Substitution Formats
Zero Code Substitution Formats
Octet
1
1
0
0
0
0
0
0
1
0
0
1
AMI
BPV
BPV
BPV
B8ZS
BPV
HDB3
B7ZS
UMC
The B8ZS line code replaces strings of 8 consecutive 0s or no pulses with the
B8ZS octet 000VB0VB, where B represents a normal bipolar pulse and V
represents a BPV. A BPV that is not part of B8ZS octet is a BPV error.
B7ZS replaces Bit 7 of all assigned time slots with a 1 if the contents are all 0.
B7ZS encoding is enabled on a per-channel basis in the Transmit Per-Channel
Control register [TPC0 to TPC31; addr 100 to 11F].
PDV 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: The enforcer never overwrites a framing bit and is not applicable during
E1 mode.
2-66
Conexant
N8370DSE
CONEXANT [ CONEXANT SYSTEMS, INC ]
