SAA7373 Datasheet, PDF (31/60 Pages) NXP Semiconductors – Digital servo processor and Compact Disc decoder CD7

Philips Semiconductors
Digital servo processor and Compact Disc
decoder (CD7)
Product specification
SAA7373
If t₁ (SUBQREADY-I status LOW to end of subcode read)
is below (2.6/n) ms, then t₂ = (13.1/n) ms [i.e. the
microcontroller can read all subcode frames if it completes
the read operation within (2.6/n) ms after the subcode is
ready]. If this criterion is not met, it is only possible to
guarantee that t₃ will be below (26.2/n) ms
(approximately).
If subcode frames with failed CRCs are present, the t₂ and
t₃ times will be increased by (13.1/n) ms for each defective
subcode frame.
It should be noted that in the lock-to-disc mode ‘n’ is
replaced by ‘d’, which is the disc speed factor.
7.15.1.6 Write servo commands
A write data command is used to transfer data (a number
of bytes) from the microcontroller, using the protocol
shown in Fig.28. 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 SAA7373 after the
HIGH-to-LOW transition of SILD; there must be a
minimum time of 70 µs between SILD pulses.
7.15.1.7 Writing repeated data in servo commands
The same data byte can be repeated by applying extra
SILD pulses as shown in Fig.29. SCL must stay HIGH
between the SILD pulses.
7.15.1.8 Read servo commands
A read data command is used to transfer data (status
information) to the microcontroller, using the protocol
shown in Fig.30. 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 µs before
reading data is started (i.e the next HIGH-to-LOW
transition on SILD); there must be a minimum time of 70 µs
between SILD pulses.
7.15.2 MICROCONTROLLER INTERFACE (I²C-BUS MODE)
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.
The sequence for a write data command (that requires
3 data bytes) is as follows;
• Send START condition
• Send address 30H (write)
• Write command byte
• Write data byte 1
• Write data byte 2.
• Write data byte 3
• 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;
• Send START condition
• Send address 30H (write)
• Write command byte
• Send STOP condition.
• Send START condition
• Send address 31H (read)
• Read data byte 1
• Read data byte 2
• Send STOP condition.
It should be noted that the timing constraints specified for
the read and write servo commands must still be adhered
to.
1998 Jul 06
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