SH7721 datasheet(814/1524 Pages) RENESAS

Part #	SH7721

Description	Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

PDF	1524 Pages

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Manufacturer	RENESAS [Renesas Technology Corp]

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814 / 1524 page

Section 22

Analog Front End Interface (AFEIF)

Rev. 3.00 Jan. 18, 2008 Page 752 of 1458

REJ09B0033-0300

22.4.3

DAA Interface

Figure 22.7 shows the blocks diagram of DAA circuit. Ringing detect and dial pulse sending

sequence are described below.

AFE_RLYCNT

AFE_RDET

AFE

(STLC7550)

AFEIF

Tip

Ring

Hyblid circuit

DC holding

circuit

Hook relay

Ringing detector

Figure 22.7

DAA Block Diagram

(1)

Ringing Detect Sequence

After the first ringing interrupt occurs, counting starts with writing 1 into RCEN bit of CTR2.

AFE must be operating before counting, because periodic counter counts AFE_FS from falling

edge to next falling edge.

The value of RCNTV register is effective only after 2nd interrupt generation, because the value of

RCNTV register is transferred from counter with a trigger of ending of 1st period cycle.

RCNTV will be 258 H (600 in decimal) if ringing cycle is 16 Hz and counted by 9600 Hz which is

default value of AFE_FS. Figure 22.8 shows detecting sequence of ringing.

SH7721 Datasheet(PDF) 814 Page - Renesas Technology Corp