saa7803 NXP Semiconductors, saa7803 Datasheet - Page 39

• Manufacturer Part Number: saa7803
• Description: Saa7803 One Chip Cd Audio Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13695
Objective data sheet
6.6.7.3 Soft mute and error detection
6.6.7.4 Hard mute on EBU
6.6.7.5 Silence detection and kill generation
Audio samples flagged as uncorrectable, neighbored by 2 good samples - or a held and a
good sample, will be interpolated. Audio samples flagged as uncorrectable, which are not
followed by a good sample, will hold the previous (correct or held) sample value.
This feature is enabled or disabled for I
The audio data going to the I
mute block. This block can ramp the audio volume down from 0 dB to 90 dB, making use
of 64 stages of about 1.5 dB each. The current stage can be monitored and changed in
software by reading or writing register MuteVolume. This allows the implementation of a
software mute-scheme. If the hardware mute logic is triggered by the error detection block
(see
3/N ms, with N the X-rate of the disc. The mute logic can be enabled separately for the
I
The back-end also contains an error detection block, that scans the data for a
programmable number (via register MuteOnDefectDelay) of consecutive corrupted stereo
samples. If such a pattern is found, and MuteConfig(MUTEERREN) is turned on, the
softmute will be triggered to start its volume ramp down. This detection will also trigger a
InterruptStatus1(AUDIOERRORDETECTED) interrupt.
The EBU can be hard muted (EBU main data and flags set to 0, status and user channel
still valid) by setting EBUConfig(EBUHARDMUTE).
The silence detector looks for 250 ms of digital silence (2’s complement data = all ’1’s or
all ’0’s) on either one or both channels and can trigger the kill-logic when it is found.
Enabling of this feature is done via KillConfig(KILLSILENCEEN).
The kill-logic generates a left and a right kill signal, which are brought out of the channel
decoder and can be used to gate the left and the right channel of an audio DAC. The kill
signals can be triggered on both channels together by the detection of stereo-silence, or
on each channel separately by the detection of mono-silence. Which operation is active
depends on the setup in register KillConfig. It is also possible to set the left and right kill
signals in software by writing directly to the KILLLEFT and KILLRIGHT bits in this register.
2
Fig 22. Error concealment on CD audio
S-bus and EBU outputs, by setting the corresponding bits in register MuteConfig.
Section
6.6.7.4), it will ramp the volume down from maximum till fully muted in
OK
interpolation
error
Rev. 01 — 19 April 2005
2
S-bus and/or EBU interface can be processed by a soft
OK
error
2
S-bus and EBU together.
hold
error
error
interpolation
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
One chip CD audio device
OK
SAA7803
001aab766
OK
39 of 74