ADV7342 datasheet(26/88 Pages) AD

26 / 88 page

ADV7342/ADV7343

Rev. 0 | Page 26 of 88

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.

SDA

SCL

START ADDR R/W ACK SUBADDRESS ACK

DATA

ACK

STOP

1–7

Figure 49. I2C Data Transfer

WRITE

SEQUENCE

READ

SEQUENCE

S SLAVE ADDR

A(S)

SUBADDR

A(S)

DATA

A(S) P

S SLAVE ADDR A(S)

SUBADDR

A(S) S SLAVE ADDR

A(S)

DATA

A(M)

A(M) P

S = START BIT

P = STOP BIT

A(S) = ACKNOWLEDGE BY SLAVE

A(M) = ACKNOWLEDGE BY MASTER

A (S) = NO-ACKNOWLEDGE BY SLAVE

A (M) = NO-ACKNOWLEDGE BY MASTER

LSB = 0

LSB = 1

A(S)

Figure 50. I2C Read and Write Sequence

SPI OPERATION

The ADV7342/ADV7343 support 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 ADV7342/ADV7343.

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 ADV7342/

ADV7343 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 ADV7342/ADV7343

remain in SPI communication mode until a reset or power-

down occurs.

To control the ADV7342/ADV7343, use the following protocol

for both read and write transactions. First, the master initiates a

data transfer by driving and holding the ADV7342/ADV7343

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 ADV7342/ADV7343 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.

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

ADV7342/ADV7343, MSB first, on the MOSI line immediately

after the starting subaddress. The data bytes are clocked into the

ADV7342/ADV7343 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 ADV7342/ADV7343 over

the MOSI line. Subsequently, 8-bit data bytes are read from the

ADV7342/ADV7343, MSB first, on the MISO line. The data

bytes are clocked out of the ADV7342/ADV7343 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.

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