RC224ATL Datasheet, PDF(77/104 Page) Conexant Systems, Inc

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RC224ATL Datasheet, PDF (77/104 Pages) Conexant Systems, Inc – EmbeddedModem Family

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RC224ATL/224ATLV

EmbeddedModem Family

6.0 Operation

6.5 Call Progress

6.5.2 Ring Detection

Ring detection is based on a digital input to the modem. External circuitry not

part of the modem is required to convert the analog 40 to 150 VRMS ring signal to

a digital single-bit data stream representation. Valid ring frequencies of 15.3 to 68

Hz are detected. Detection is achieved by counting valid high to low ring signal

transitions. Valid transitions consist of a high state of 2 to 34 ms followed by a low

state of 2 to 42 ms. Ring signals that have transition counts less than the nominal

value are discarded.

In addition to valid high to low transitions, ring detection depends on the

cadence of the ring ON time (valid transitions occurring) and ring OFF time (no

valid transitions). Ring OFF times must be greater than 0.5 seconds. Ring ON

times must be greater than 125 ms at 20 Hz (100 ms at 68 Hz).

Ring detection is integrated over 8 seconds. All counters and timers are reset

at 8 second intervals. The modem will answer the ring after N valid ON/OFF ring

cycles. N is programmable via the S0 register. Upon detecting N rings, the

modem verifies that the current ring state has been in the OFF state for 0.5

seconds before seizing the line.

Table 6-5 lists the Fax Class 1 calling sequence; Table 6-6 lists the answering

sequence.

Table 6-5. Fax Class 1 Calling Sequence (1 of 2)

DTE Commands

(Host)

DCE Responses

(Modem)

Remote Fax

(1) AT+FCLASS=1

(2) OK

(3) ATDT6163

(4) Dials

(6) CONNECT

PHASE A

(5) Answers

(7) Send HDLC flags

PHASE B

(8) Send NSF frame

(9) <NSF>, OK

(10) AT+FRH=3

(11) CONNECT

(12) Send CSI frame

(13) <CIS>, OK

(14) AT+FRH=3

(15) CONNECT

(16) Send DIS frame

(19) AT+FTH=3

(17) <DIS>, OK

(20) Send HDLC flags

(21) CONNECT

(18) Drop carrier

(21) Receive flags

(22) <TSI>

(23) Send TSI frame

(24) Receive TSI

(25) CONNECT

(26) <DCS>

(27) Send DCS frame

(29) Detect last frame bit

(28) Received DCS

Notes

Set to Class 1

+FRH=3 implied by Dialing

Last frame bit = 1

Last frame bit = 0

Last frame bit = 1

D224ATLVDSC

Conexant

6-13

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