adv7344 Analog Devices, Inc., adv7344 Datasheet - Page 26

• Manufacturer Part Number: adv7344
• Description: Multiformat Video Encoder Six 14-bit Noise Shaped Video Dacs
• Manufacturer: Analog Devices, Inc.

ADV7344
Figure 49 shows an example of data transfer for a write sequence and the start and stop conditions. Figure 50 shows bus write and read
sequences.
SPI OPERATION
The ADV7344 supports a 4-wire serial (SPI-compatible) bus
connecting multiple peripherals. Two inputs, master out slave in
(MOSI) and serial clock (SCLK), and one output, master in
slave out (MISO), carry information between a master SPI
peripheral on the bus and the ADV7344. Each slave device on
the bus has a slave select pin that is connected to the master SPI
peripheral by a unique slave select line. As such, slave device
addressing is not required.
To invoke SPI operation, a master SPI peripheral (for example, a
microprocessor) should issue three low pulses on the ADV7344
ALSB/ SPI_SS pin. When the encoder detects the third rising
edge on the ALSB/ SPI_SS pin, it automatically switches to SPI
communication mode. The ADV7344 remains in SPI
communication mode until a reset or power-down occurs.
To control the ADV7344, use the following protocol for both
read and write transactions. First, the master initiates a data
transfer by driving and holding the ALSB/ SPI_SS pin low. On
the first SCLK rising edge after ALSB/ SPI_SS has been driven low,
the write command, defined as 0xD4, is written to the ADV7344
over the MOSI line. The second byte written to the MOSI line is
interpreted as the starting subaddress. Data on the MOSI line is
written MSB first and clocked on the rising edge of SCLK.
SEQUENCE
SEQUENCE
WRITE
READ
S SLAVE ADDR A(S)
S
S = START BIT
P = STOP BIT
SLAVE ADDR A(S)
SDA
SCL
LSB = 0
START ADDR R/W ACK SUBADDRESS ACK
A(S) = ACKNOWLEDGE BY SLAVE
A(M) = ACKNOWLEDGE BY MASTER
S
SUBADDR
SUBADDR
1–7
8
Figure 50. I
A(S)
A(S) S SLAVE ADDR
9
Figure 49. I
Rev. 0 | Page 26 of 88
2
DATA
1–7
C Read and Write Sequence
2
C Data Transfer
8
LSB = 1
A(S)
A (S) = NO-ACKNOWLEDGE BY SLAVE
A (M) = NO-ACKNOWLEDGE BY MASTER
9
A(S)
There is a subaddress auto-increment facility. This allows data
to be written to or read from registers in ascending subaddress
sequence starting at any valid subaddress. The user can also
access any unique subaddress register on a one-by-one basis.
In a write data transfer, 8-bit data bytes are written to the
ADV7344, MSB first, on the MOSI line immediately after the
starting subaddress. The data bytes are clocked into the ADV7344
on the rising edge of SCLK. When all data bytes have been
written, the master completes the transfer by driving and
holding the ALSB/ SPI_SS pin high.
In a read data transfer, after the subaddress has been clocked in
on the MOSI line, the ALSB/ SPI_SS pin is driven and held high
for at least one clock cycle. Then, the ALSB/ SPI_SS pin is driven
and held low again. On the first SCLK rising edge after
ALSB/ SPI_SS has been driven low, the read command, defined
as 0xD5, is written, MSB first, to the ADV7344 over the MOSI
line. Subsequently, 8-bit data bytes are read from the ADV7344,
MSB first, on the MISO line. The data bytes are clocked out of
the ADV7344 on the falling edge of SCLK. When all data bytes
have been read, the master completes the transfer by driving
and holding the ALSB/ SPI_SS pin high.
DATA
1–7
DATA
8
ACK
DATA
9
A(M)
STOP
P
A(S) P
DATA
A(M) P