RS8953 Conexant Systems, Inc., RS8953 Datasheet - Page 81

• Manufacturer Part Number: RS8953
• Description: High-bit-rate Digital Subscriber Line (hdsl) Channel unit
• Manufacturer: Conexant Systems, Inc.

RS8953B/8953SPB
HDSL Channel Unit
HOH_EN
FORCE_ONE
TX_ERR_EN
HH_LOOP
SCR_TAP
SLV_STUF
TAUX_EN
N8953BDSB
0x07—Transmit Command Register 2 (TCMD_2)
—
7
STUF_CNTR_
HDSL Overhead Enable—The HOH multiplexer inserts EOC, IND, and CRC bits. Otherwise,
transmit overhead bits, except SYNC and STUFF, are forced to all 1s. HOH_EN = 0 select
transmission of two-level or four-level scrambled 1s.
Force All 1s Payload—Transmit payload data bytes are replaced by all 1s. FORCE_ONE and
HOH_EN are both set to enable output of a four-level framed, scrambled-1s signal.
Transmit Error Interrupt Enable—Transmit errors request TX_ERR interrupt and report
TXn_ERR status upon detection of TFIFO or TSTUFF errors [STATUS_3; addr 0x07].
Disabled channels are prevented from activating INTR*, or setting TX_ERR [IRR; addr
0x1F]. Transmit errors are always latched in ERR_STATUS [addr 0x3C] regardless of
TX_ERR_EN.
Loopback to HDSL on the HDSL Side—Receive HDSL data (RDATn) is switched to transmit
HDSL data (TDATn) to accomplish a loopback of the HDSL channel on the HDSL side.
Loopback data is switched at I/O pins and does not alter HDSL receive operations.
Scrambler Tap—Selects which delay stage, 5th or 18th, to tap for feedback in the transmit
scrambler. The system’s HDSL terminal type dictates which scrambler tap should be selected.
Slave STUFF Bits—Transmit STUFF bits are either generated by a local stuffing mechanism
or are slaved to an alternate source of STUFF bits. If enabled, the slave STUFF source is
chosen by STUFF_SEL in Common CMD_5 [addr 0xE9].
Transmit Auxiliary Enable—Transmit auxiliary data from the TAUX1–TAUX3 inputs are
sampled when the respective TLOAD1–TLOAD3 outputs are active. TAUX samples and
TLOAD activation are selected for each payload byte via the transmit payload map [TMAP;
addr 0x08]. When TAUX_EN is low, TAUX inputs are ignored and TLOAD outputs are forced
low.
MODE
6
EXT_ZBIT
5
0 = HOH transmitted as all 1s
1 = Normal HOH transmission
0 = Normal payload transmission
1 = Force all 1s payload
0 = Disable transmit error interrupts
1 = Enable transmit error interrupts
0 = Normal transmit
1 = TDATn supplied by RDATn pin
0 = HTU-C or LTU terminal type, scrambler taps 5th delay stage
1 = HTU-R or NTU terminal type, scrambler taps 18th delay stage
0 = Local STUFF bit generation
1 = Slave STUFF bits to STUFF_SEL source
0 = Disable TAUX and TLOAD signals
1 = Enable TAUX and TLOAD signals
REPEAT_EN
4
Conexant
TAUX_EN
3
SLV_STUF
2
SCR_TAP
1
4.2 HDSL Transmit
4.0 Registers
HH_LOOP
0
4-13