SAA7824 Datasheet, PDF (36/89 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
7.17 Microcontroller interface
Communication on the microcontroller interface can be
set-up in three different modes:
• 4-wire bus mode: where:
– SCL = serial clock
– SDA = serial data
– RAB = R/W control and data strobe (active HIGH) for
writing to decoder registers 0 to F, reading status bit
selected via decoder register 2 and reading
Q-channel subcode
– SILD = R/W control and data strobe (active LOW) for
servo commands
• 3-wire bus mode: where:
– SCL = serial clock
– SDA = serial data
– RAB = not used, pulled LOW
– SILD = R/W control and data strobe (active LOW) for
servo commands
• I²C-bus mode: I²C-bus protocol where the SAA7824
behaves as slave device, activated by setting
RAB = HIGH and SILD = LOW where:
– I²C-bus slave address (write mode) = 30H
– I²C-bus slave address (read mode) = 31H
– Maximum data transfer rate = 400 kbits/s.
It should be noted that when using the I²C-bus mode, only
servo commands can be used. Therefore, writing to
decoder registers 0 to F, reading decoder status and
reading Q-channel subcode data must be performed by
servo commands.
The 3-wire mode is very similar to the 4-wire mode, except
that all communication to the decoder is via the servo.
Communication to the servo uses the same hardware
protocol and timing as the 4-wire mode.
Extra servo commands exist for read and write access to
the decoder via the internal decoder interface. The internal
interface must be enabled by using the xtra_preset
command. RAB is not used and must be tied LOW;
see Fig.23
handbook, halfpage
MICROCONTROLLER
INTERFACE
(DECODER)
SAA7824
RAB = LOW
MICROCONTROLLER
INTERFACE
SDA
SCL
SILD
MDB502
Fig.23 Microcontroller interface for the 3-wire mode.
2003 Oct 01
36