SAA7324 Datasheet, PDF (16/68 Pages) NXP Semiconductors – Digital servo processor and Compact Disc decoder with integrated DAC CD10 II

Philips Semiconductors
Digital servo processor and Compact Disc
decoder with integrated DAC (CD10 II)
Product specification
SAA7324
7.7.4 MUTE, FULL-SCALE, ATTENUATION AND FADE
A digital level controller is present on the SAA7324 which
performs the functions of soft mute, full-scale, attenuation
and fade; these are selected via decoder register 0:
• Mute: signal reduced to 0 in a maximum of 128 steps;
(3/n) ms
• Attenuation: signal scaled by −12 dB
• Full-scale: ramp signal back to 0 dB level; from mute
takes (3/n) ms
• Fade: activates a 128 stage counter which allows the
signal to be scaled up/down by 0.07 dB steps
– 128 = full-scale
– 120 = −0.5 dB (i.e. full-scale if oversampling filter
used)
– 32 = −12 dB
– 0 = mute.
7.7.5 PEAK DETECTOR
The peak detector measures the highest audio level
(absolute value) on positive peaks for left and right
channels. The 8 most significant bits are output in the
Q-channel data in place of the CRC bits. Bits 81 to 88
contain the left peak value (bit 88 = MSB) and
bits 89 to 96 contain the right peak value (bit 96 = MSB).
The values are reset after reading Q-channel data via pin
SDA.
Interpolation
Hold
Interpolation
OK
Error
OK
Error
Error
Error
OK
OK
MGA372
Fig.11 Concealment mechanism.
2000 Jun 26
16