SAA7345 データシートの表示（PDF） - Philips Electronics

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SAA7345

CMOS digital decoding IC with RAM for Compact Disc

Philips Electronics 

Philips Semiconductors

CMOS digital decoding IC with RAM for

Compact Disc

Product specification

SAA7345

RAB

(microcontroller)

CL

(microcontroller)

DA

(microcontroller)

DA (SAA7345)

high impedance

STATUS

Fig.7 SAA7345 status READ timing.

MGA381 - 1

READING Q-CHANNEL SUBCODE FROM SAA7345

To read Q-channel subcode from SAA7345, the SUBQREADY-I signal should be selected as status signal. The subcode

read timing is shown in Fig.8.

Read subcode operation sequence

• Monitor SUBQREADY-I status signal.

• When this signal is LOW, and up to 2.3 ms after its LOW-to-HIGH transition, it is permitted to read subcode.

• Set CL LOW, SAA7345 will output first subcode bit (Q1).

• After subcode read starts, the microcontroller may take as long as it wants to terminate read operation.

• SAA7345 will output consecutive subcode bits after each HIGH-to-LOW transition of CL.

• When enough subcode has been read (1 to 96 bits), stop reading by pulling RAB LOW.

RAB

(microcontroller)

CL

(microcontroller)

DA (SAA7345)

CRC

OK Q1 Q2 Q3

STATUS

Qn–2 Qn–1 Qn

MGA382 - 1

Fig.8 SAA7345 Q-channel subcode READ timing.

PEAK DETECTOR OUTPUT

In place of the CRC-bits (bits 81 to 96), the peak detector information is added to the Q-channel data. The peak

information corresponds to the highest audio level (absolute value) and is measured on positive peaks. Only the most

significant 8 bits of the peak level are given, in unsigned notation. Bits 81 to 88 contain the LEFT peak value

(bit 88 = MSB) and bits 89 to 96 contain the RIGHT channel (bit 96 = MSB). Value is reset after reading Q-channel data.

1998 Feb 16

9

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