RS8953B/8953SPB
3.0 Circuit Descriptions
HDSL Channel Unit
3.5 HDSL Channel
In T1 framing mode [E1_MODE = 0 in CMD_1; addr 0xE5], Z-bit positions
are replaced by F-bits and are treated as payload with respect to the PCM channel.
Figure 3-16 shows a standard application 2T1 frame format in which each
payload block contains 1 F-bit, plus 12 payload bytes. The figure also illustrates
F-bits routed as payload to both HDSL channels and demonstrates the order in
which PCM timeslots are routed to payload bytes: bytes 1 through 12 correspond
to PCM timeslots 1–12 routed on CH1, bytes 13 through 24 correspond to PCM
timeslots 13–24 routed on CH2. CH3 is unused in 2T1 application.
Standard application 2E1 and 3E1 frame formats are shown in Figure 3-17
and Figure 3-18, respectively. Standard mapping of PCM data places alternating
bytes in each HDSL channel, as shown by byte numbering. The 2E1 payload
block contains 18 payload bytes, and the 3E1 payload block contains 12 bytes. In
E1 framing mode [E1_MODE = 1 in CMD_1; addr 0xE5], 48 Z-bits are treated as
overhead and are under MPU control. (Refer to Table 3-5 for Z-bit definitions).
Table 3-3 shows additional examples of frame mapping options.
Figure 3-16. 2T1 Frame Format
2T1 FRAME
2351 OR 2353 QUATS
7Q
1Q
12 X 48.5 = 582Q 5Q
582Q
5Q
582Q
5Q
582Q
0,2Q
S
Q
1
S
Q
2
H
O
H
B
0
1
B
0
2
B
1
2
H
O
H
B
1
3
B
1
4
B
2
4
H
O
H
B
2
5
B
2
6
B
3
6
H
O
H
B
3
7
B
3
8
B
4
8
S
Q
1
S
Q
2
SYNC
WORD
SYNC
WORD
“6-”
“6+”
1/392 MS
F
BYTE1
8-BITS
BYTE2
BYTE3
BYTE12
BYTE24
0 MS
CH1
CH2
6 MS
LEGEND:
1B
F
BNN = PAYLOAD BLOCKS 1-48
HOH = HDSL OVERHEAD
SQN = STUFF QUAT
BYTE13
BYTE14
BYTE15
BNN
97/784 MS
N8953BDSB
Conexant
3-21
CONEXANT [ CONEXANT SYSTEMS, INC ]
