SAA7374GP PHILIPS [NXP Semiconductors], SAA7374GP Datasheet - Page 30

• Manufacturer Part Number: SAA7374GP
• Description: Low voltage digital servo processor and Compact Disc decoder CD7LV
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
7.15
Communication on the microcontroller interface can be
set-up in two different modes;
1. 4-wire bus mode: protocol compatible with SAA7345
2. I
It should be noted that only servo commands can be used
therefore, writing to registers 0 to F, reading decoder
status and reading Q-channel subcode data must be
performed by servo commands.
7.15.1
7.15.1.1
The sixteen 4-bit programmable configuration registers,
0 to F (see Table 12), can be written to via the
microcontroller interface using the protocol shown in
Fig.22.
It should be noted that SILD must be held HIGH; A3 to A0
identifies the register number and D3 to D0 is the data; the
data is latched into the register on the LOW-to-HIGH
transition of RAB.
7.15.1.2
The same data can be repeated several times (e.g. for a
fade function) by applying extra RAB pulses as shown in
Fig.23. It should be noted that SCL must stay HIGH
between RAB pulses.
7.15.1.3
There are several internal status signals, selected via
register 2, which can be made available on the SDA line;
1998 Feb 26
SUBQREADY-I: LOW if new subcode word is ready in
Q-channel register.
Low voltage digital servo processor and
Compact Disc decoder (CD7LV)
(CD6) and TDA1301 (DSIC2) where;
a) SCL = serial bit clock.
b) SDA = serial data.
c) RAB = R/W control and data strobe (active HIGH)
d) SILD = R/W control and data strobe (active LOW)
behaves as slave device. Activated by setting
RAB = HIGH and SILD = LOW where;
a) I
b) I
c) Maximum data transfer rate = 400 kbits/s.
2
C-bus mode: I
Microcontroller interface
for writing to registers 0 to F, reading status bit
selected via register 2 and reading Q-channel
subcode.
for servo commands.
2
2
MICROCONTROLLER INTERFACE
C-bus slave address (write mode) = 30H.
C-bus slave address (read mode) = 31H.
Writing data to registers 0 to F
Writing repeated data to registers 0 to F
Reading decoder status information on SDA
2
C-bus protocol where SAA7374
(4-
WIRE BUS MODE
)
30
The status read protocol is shown in Fig.24. It should be
noted that SILD must be held HIGH.
7.15.1.4
To read the Q-channel subcode direct in the 4-wire bus
mode, the SUBQREADY-I signal should be selected as
status signal. The subcode read protocol is illustrated in
Fig.25.
It should be noted that SILD must be held HIGH; after
subcode read starts, the microcontroller may take as long
as it wants to terminate the read operation; when enough
subcode has been read (1 to 96 bits), terminate reading by
pulling RAB LOW.
Alternatively, the Q-channel subcode can be read using a
servo command as follows;
7.15.1.5
When the CRC of the Q-channel word is good, and no
subcode is being read, the SUBQREADY-I status signal
will react as shown in Fig.26.
When the CRC is good and subcode is being read, the
timing in Fig.27 applies.
MOTSTART1: HIGH if motor is turning at 75% or more
of nominal speed.
MOTSTART2: HIGH if motor is turning at 50% or more
of nominal speed.
MOTSTOP: HIGH if motor is turning at 12% or less of
nominal speed. Can be set to indicate 6% or less
(instead of 12% or less) via register E.
PLL Lock: HIGH if sync coincidence signals are found.
V1: follows input on V1 pin.
V2: follows input on V2 pin.
MOTOR-OV: HIGH if the motor servo output stage
saturates.
FIFO-OV: HIGH if FIFO overflows.
SHOCK: MOTSTART2 + PLL Lock + MOTOR-OV +
FIFO-OV + servo interrupt signal + OTD (HIGH if shock
detected)
LA-SHOCK: latched SHOCK signal
Use the read high-level status command to monitor the
subcode ready signal
Send the read subcode command, and read the
required number of bytes (up to 12)
Send the read high-level status command; to re-enable
the decoder interface.
Reading Q-channel subcode
Behaviour of the SUBQREADY-I signal
Product specification
SAA7374