3.0 Circuit Descriptions
RS8953B/8953SPB
3.5 HDSL Channel
HDSL Channel Unit
The MPU can bypass the STUFF generator and select an alternate source of
transmit STUFF bits by setting SLV_STUF [TCMD_2; addr 0x07] and selecting
the alternate source in STUFF_SEL [CMD_5; addr 0xE9]. Alternate STUFF bits
can be supplied by other HDSL channels, or the MPU can directly manipulate
EXT_STUFF [CMD_5; addr 0xE9]. For systems that externally synchronize
PCM and HDSL clock phase, the STUFF generator can also be programmed to
insert an alternating pattern of 0 and 4 STUFF bits.
3.5.1.6 2B1Q Encoder
The 2B1Q (2 Binary, 1 Quaternary) encoder provides the ability to directly
interface to the Conexant HDSL transceiver. The 2B1Q encoder converts HDSL
data generated internally at the bit rate into sign and magnitude data according to
the quaternary alignment provided on the QCLKn input. (Refer to Table 3-4 for
sign and magnitude bits used to generate 2B1Q coded outputs on TDATn.)
Table 3-4. 2B1Q Encoder Alignment
First Bit
(Sign)
Second Bit
(Magnitudes)
Quaternary Symbol
(Quat)
1
1
0
0
0
1
1
0
+3
+1
–1
–3
Table 3-5. Z-Bit Definitions
Z-bit
Loop1
(Zn)
Loop2
Loop3
Comments
1
1
0
0
x
x
x
x
x
x
x
0
1
0
x
x
x
x
x
x
x
0
0
1
x
x
x
x
x
x
x
Pair Identification
Pair Identification
Pair Identification
Not defined
2
3
4
5
6
Not defined
Not defined
7
Not defined
8 to 46
47
Not defined
Not defined
48
Not defined
3-26
Conexant
N8953BDSB
CONEXANT [ CONEXANT SYSTEMS, INC ]
