
MT9071
Preliminary Information
38
Figure 8 - DS1 Link Frame Format
The first bit of a DS1 frame is reserved for basic frame alignment, D4 and ESF multiframe alignment and the
communication of maintenance information (data link). The remaining 24 timeslots (referred to as channels)
carry either PCM encoded voice signals or digital data. Channel alignment and bit numbering is consistent with
timeslot alignment and bit numbering. Also see Table 28 - T1 DS1 & ST-BUS DSTi/DSTo Timeslot Relationship.
4.1.1
Numerous encoding options are selectable in the transmit direction with control register bit TZCS2-0 and
TXB8ZS (see Table 80 - T1 Line Coding Control - R/W Address Y01), these include:
T1 Encoding and Decoding Options
No Zero Code Suppression.
GTE Zero Code Suppression (bit 8 of an all zero channel byte is replaced by a one, except in signaling
frames where bit 7 is forced to a one).
DDS Zero Code Suppression (an all zero byte is replaced by 10011000).
Bell Zero Code Suppression (bit 1, second bit of an all zero channel is replaced by a one).
Jammed Bit 8 (bit 0 of all channels are replaced by a one).
B8ZS.
Numerous decoding options are selectable in the receive direction with control register bits RZCS2-0 and
RXB8ZS (see Table 80 - T1 Line Coding Control - R/W Address Y01), these include:
No Zero Code Suppression.
GTE Zero Code Suppression (bit 8 of an all zero channel byte is replaced by a one, except in signaling
frames where bit 7 is forced to a one).
DDS Zero Code Suppression (an all zero byte is replaced by 10011000).
Bell Zero Code Suppression (bit 1, second bit of an all zero channel is replaced by a one).
B8ZS.
Note: If a suppression code is enabled for a channel the B8ZS coding will not take place for the channel.
Although 8 consecutive zeros in a non-channel boundary will be subjected to B8ZS suppression. Note that the
bit designations are with respect to the PCM24 side where bit 1 is sent and received first. In all cases, Alternate
Mark Inversion (AMI) is used in both transmit and receive directions.
FRAME
1
FRAME
12
FRAME
11
FRAME
1
FRAME
12
D4 MULTIFRAME FRAME - 1.5ms
DS0 CHANNEL (8/1.544)us
CHANNEL
1
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
CHANNEL
24
CHANNEL
23
CHANNEL
1
S
BIT
S
BIT
CHANNEL
24
DS1 FRAME - 125us
(1/1.544)us