155
DSP for CD and DVD-ROM systems
SAA7335
Microcontroller interface
The SAA7335 has two microcontroller interfaces, one
serial I
2
C-bus and one parallel (8051 microcontroller
compatible).
The two communication modes may be operated at the
same time, the modes are described below:
1. Parallel mode: protocol compatible with 8052
multiplexed bus:
a) da0 to da7 = address/data bus
b) ALE = Address Latch Enable, latches the address
information on the bus
c)
WRi = active LOW write signal for write to
SAA7335
d)
RDi = active LOW read signal for read from
SAA7335
e) CSi = active HIGH Chip Select signal (this signal
gates the
RDi and WRi signals).
2. I
2
C-bus mode: I
2
C-bus protocol where SAA7335
behaves as slave device where:
a) SDA = I
2
C-bus data
b) SCL = I
2
C-bus clock
c) I
2
C-bus slave address (write mode) = 3EH
d) I
2
C-bus slave address (read mode) = 3FH
e) Maximum data transfer rate = 400 kbits/s.
M
ICROCONTROLLER INTERFACE
(I
2
C-
BUS MODE
)
Bytes are transferred over the interface in single bytes of
which there are two types; write data commands and read
data commands.
The sequence for a write data command (1 data byte) is as
follows:
Send START condition
Send address 3EH (write)
Write command address byte
Write data byte
Send STOP condition.
The sequence for a read data command (that reads 1 data
byte) is as follows:
Send START condition
Send address 3EH (write)
Write status address byte
Send STOP condition
Send START condition
Send address 3FH (read)
Read data byte
Send STOP condition.
R
EADING AND WRITING DATA TO THE
SAA7335
The SAA7335 has 32 x 8-bit configuration and status
registers as shown in Table 1. Not all locations are
currently defined and some remain reserved for future
upgrades. These can be written to or read from via the
microcontroller interface using either the serial or parallel
control bus.
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