BT8954 CONEXANT [Conexant Systems, Inc], BT8954 Datasheet - Page 12

• Manufacturer Part Number: BT8954
• Description: VOICE PAIR GAIN FRAMER
• Manufacturer: CONEXANT [Conexant Systems, Inc]

1.0 DSL Systems
1.1 Voice Pair Gain Applications
Figure 1-1. Block Diagram of a PCM4 Voice Pair Gain Modem
1.1.1 Repeaters
1-2
Hybrid
Microcomputer
Bt8960/70
Bit Pump
gain modem is illustrated in
codec and Subscriber Line Interface Circuit (SLIC) chips for each channel
perform the transmit encoding (A/D conversion) and receive decoding (D/A
conversion) of voice signals. The time-division multiplexing of the voice signals
on the PCMT and PCMR serial buses is as follows: Bt8954 informs PCM
Codec_n with the PCMFn frame sync when to expect the next byte from Bt8954
on the PCMR bus, and when to put its next byte on the PCMT bus. In this way,
Bt8954 uses the PCMFn frame sync to designate the time slot that Codec_n has
access to the PCMR and PCMT buses.
Figure 1-2
Office and remote terminals to extend the transmission distance. For each Bt8954
repeater, the BCLK/QCLK is connected to the BCLK/QCLK of its source
transceiver while the BCLK_REP/QCLK_REP is connected to the BCLK/QCLK
of its destination transceiver. The Central Office Bt8954 gets its
HCLK/BCLK/QCLK from the Central Office transceiver, which generates them
from a free-running crystal. The repeater transceiver connected to the Central
Office recovers its HCLK, BCLK, and QCLK from the HDSL line. These signals
then drive the HCLK, BCLK, and QCLK pins of the Central Office to Remote
Terminal Bt8954, and the HCLK, BCLK_REP, and QCLK_REP pins of the
Remote Terminal to Central Office Bt8954. The repeater transceiver connected to
the Remote Terminal receives HCLK from the repeater transceiver connected to
the Central Office. The repeater transceiver connected to the Remote Terminal
generates BCLK/QCLK and drives the BCLK/QCLK pins of the Remote
Terminal to Central Office Terminal Bt8954. The repeater transceiver drives the
BCLK_REP/QCLK_REP pins of the Central Office Terminal to Remote
Terminal Bt8954.
from the bit pump is descrambled.
Bt8954’s position among the key elements of a PCM4 (4-channel) voice pair
In Repeater Mode, the Bt8954 does not use the FIFOs. First, data received
QCLK
BCLK
RDAT
TDAT
illustrates a pair of Bt8954 repeaters placed in line between Central
VPG Framer
Bt8954
Conexant
Logic
PCMCLK
Figure
PCMR
PCMF4
PCMT
1-1. The Pulse Code Multiplexed (PCM)
PCMF1
FSX1/FSR1
FSX4/FSR4
CODEC1
CODEC4
Voice Pair Gain Framer
.
C1 C2 DET* E0
C1 C2 DET* E0
SLIC1
SLIC4
N8954DSC
Bt8954