BT8954 CONEXANT [Conexant Systems, Inc], BT8954 Datasheet - Page 41

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

Bt8954
Voice Pair Gain Framer
3.7.4 COTF Receiver Synchronization
Figure 3-19. COTF Receiver Synchronization
3.7.5 Round Trip Delay
N8954DSC
TPCM_125 s
RPCM_6 ms
RDSL_6 ms
RDAT
SYNC_WORD
RFIFO_WL.RT
The RDSL_6ms signal in the COTF is generated after SYNC_WORD has been
detected as illustrated in
RDSL_6ms by RFIFO_WL.RT (RFIFO Water Level in the RTF) plus time to
realign to the next TPCM_125 s. At the Central Office, the PCM receive frames
are slaved to the DSL frame timing and aligned to the transmit PCM_125 s
frame. The re-alignment time is added because the same PCM frame SYNC
signal is used for transmitting and receiving PCM frames from the PCM codecs.
The microcomputer determines the round-trip delay by measuring the time that
elapses between the Tx and Rx interrupts in the Interrupt Status register
[ISR; 0xD0] at the Central Office.
TPCM_125 s
125 s
Realign to
Conexant
6 ms
Figure
3-19. RPCM_6ms is phase-offset from
6 ms
SYNC_WORD
125 s
3.0 Circuit Descriptions
3.7 Synchronization
3-19