saa7824 NXP Semiconductors, saa7824 Datasheet - Page 39

• Manufacturer Part Number: saa7824
• Description: Cd Audio Decoder, Digital Servo And Filterless Dac With Integrated Pre-amp And Laser Control Phonic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.17.1.7
A write data command is used to transfer data (a number
of bytes) from the microcontroller, using the protocol
illustrated in Fig.31. The first of these bytes is the
command byte and the following are data bytes; the
number (between 1 and 7) depends on the command
byte.
It should be noted that RAB must be held LOW; the
command or data is interpreted by the SAA7824 after the
HIGH-to-LOW transition of SILD; there must be a
minimum time of 70 s between SILD pulses.
7.17.1.8
The same data byte can be repeated by applying extra
SILD pulses as illustrated in Fig.32. SCL must be HIGH
between the SILD pulses.
7.17.1.9
A read data command is used to transfer data (status
information) to the microcontroller, using the protocol
shown in Fig.33. The first byte written determines the type
of command. After this byte a variable number of bytes can
be read. It should be noted that RAB must be held LOW;
after the end of the command byte (LOW-to-HIGH
transition on SILD) there must be a delay of 70 s before
data can be read (i.e. the next HIGH-to-LOW transition on
SILD) and there must be a minimum time of 70 s between
SILD pulses.
7.17.2
Bytes are transferred over the interface in groups (i.e.
servo commands) of which there are two types: write data
commands and read data commands.
2003 Oct 01
handbook, full pagewidth
CD audio decoder, digital servo and filterless
DAC with integrated pre-amp and laser control
M
Write servo commands
Writing repeated data in servo commands
Read servo commands
ICROCONTROLLER INTERFACE
(microcontroller)
(microcontroller)
(microcontroller)
(SAA782X)
SDA
SCL
SDA
RAB
Fig.25 Microcontroller write protocol for registers 0 to F.
(I
A3
2
C-
BUS MODE
A2
A1
)
high-impedance
A0
39
The sequence for a write data command (that requires
3 data bytes) is as follows:
1. Send START condition.
2. Send address 30H (write).
3. Write command byte.
4. Write data byte 1.
5. Write data byte 2.
6. Write data byte 3.
7. Send STOP condition.
It should be noted that more than one command can be
sent in one write sequence.
The sequence for a read data command (that reads 2 data
bytes) is as follows:
1. Send START condition.
2. Send address 30H (write).
3. Write command byte.
4. Send STOP condition.
5. Send START condition.
6. Send address 31H (read).
7. Read data byte 1.
8. Read data byte 2.
9. Send STOP condition.
It should be noted that the timing constraints specified for
the read and write servo commands must still be adhered
to.
D3
D2
D1
D0
Product specification
MBL445
SAA7824