User guide

August 2001 237

R2-CCITT

Table 43 shows the pattern of bits transmitted by the CO and

CPE in the R2-CCITT protocol.

Table 43. R2-CCITT: CO Calls CPE

In the R2-CCITT line protocol, bits C and D are fixed, C=0, D=1.

Both ends transmit 10 in the idle state. The CO seizes the line

with 00, which it continues to transmit throughout the call. The

CPE acknowledges the seizure with 11. It continues to transmit

11 through the inter-register signaling, then transmits 01 to

answer the call. At the end of the call, the CPE transmits a 11

to clear the line, then returns to idle.

All bit transitions are recognized after the time specified by

RDG_LINE_DEGLITCH_TIME parameter.

Status CO CPE Timing Parameter

Idle 10 10

Seizure 00 --> 10

Acknowledgment 00 <-- 11 RDG_LOCAL_MIN_SEIZURE_ACK,

RDG_LOCAL_ACK_GUARD_TIME

R2 Inter-register

Signaling

00 11

Answer 00 <-- 01 RDG_LOCAL_ANSWER_DUR,

RDG_LOCAL_ANSWER_GUARD_TIME

Conversation 00 01

Clear Back 00 <-- 11 RDG_LOCAL_CLEAR_BACK_DUR

Clear Forward 10 --> 11 RDG_LOCAL_CLEAR_BACK_DUR

Release 10 <-- 10

Blocked 10 11

Hook Flash 00 <-- 01/11/01 RDG_LOCAL_FLASH_DUR

00/10/00 --> 01

Forced Release 00 <-- 00