SAA7824 Datasheet, PDF (24/89 Pages) NXP Semiconductors – CD audio decoder, digital servo and filterless DAC with integrated pre-amp and laser control (PhonIC)

Philips Semiconductors
CD audio decoder, digital servo and filterless
DAC with integrated pre-amp and laser control
Product specification
SAA7824
Table 10 Bit assignment
FUNCTION
Control
BITS
0 to 3
Reserved mode
Category code
Clock accuracy
Remaining
4 to 7
8 to 15
28 to 29
6 to 27 and
30 to 191
DESCRIPTION
copy of CRC checked Q-channel control bits 0 to 3; bit 2 is logic 1 when copy
permitted; bit 3 is logic 1 when recording has pre-emphasis
always zero
CD: bit 8 = logic 1, all other bits = logic 0
set by register A; 10 = level I; 00 = level II; 01 = level III
always zero
7.12 KILL features
7.12.1 THE KILL CIRCUIT
The KILL circuit detects digital silence by testing for an
all-zero or all-ones data word in the left and right channels.
This occurs in two places; prior to the digital filter (internal
KILL), and in the digital DAC (loopback/external KILL).
Programming bit 3 of new shadow register A (bank 2)
determines whether internal or external data is used. The
output is switched to active HIGH when silence has been
detected for at least 270 ms, or if mute is active, or in
CD-ROM mode. Two KILL modes are available which can
be selected by decoder register C:
• Mono KILL: LKILL and RKILL are both active HIGH
when silence is detected on left and right channels
simultaneously
• Stereo KILL: LKILL and RKILL are active HIGH
independently of each other when silence is detected on
either channel.
7.12.2 SILENCE INJECTION
The silence inject function monitors the left and right KILL
signals and forces the analog DAC into silence when KILL
is asserted. This improves the internal Signal-to-Noise
Ratio (SNR) by preventing any spurious noise from
reaching the DAC. The silence inject function can be
enabled or disabled by programming bit 2 of the new
shadow register A (bank 2).
7.13 Audio features off
The audio features can be turned off (selected by decoder
register E) and will affect the following functions:
• Digital filter, fade, peak detector, internal KILL circuit
(although RKILL and LKILL outputs still active) are
disabled
• V5 (if selected to be the de-emphasis flag output) and
the EBU outputs become undefined.
The EBU output should be set LOW prior to switching the
audio features off and after switching the audio features
back on, a full-scale command should be given.
7.14 The versatile pins interface
The SAA7824 has five pins that can be reconfigured for
different applications.
The functions of these versatile pins are identical to the
SAA732x series and can be programmed by decoder
registers C, D and shadow register 3 (bank 1) as shown in
Table 11.
2003 Oct 01
24