VT5366

Serial control bus

19/30

The byte following the address byte contains the address of the first data byte (also referred

to as the

Figure 9.

Serial interface data format (write ex)

6.2.2

Message interpretation

All serial interface communications with the sensor must begin with a

place. The sensor will acknowledge the receipt of a valid address by driving the

low. The state of the

data, sampled from

During a write sequence the second byte sent is an address index and is used to point to

one of the internal registers. The receiver will automatically increment the index address by

one location after each slave acknowledge. The master can therefore send data bytes

continuously to the slave until the slave fails to provide an acknowledge or the master

terminates the write communication with a

As data is received by the slave it is written bit by bit to a serial/parallel register. After each

data byte has been received by the slave, an acknowledge is generated, the data is then

stored in the internal register addressed by the current index.

During a read message, the next byte read from the slave device are the contents of the

register addressed by the current index. The contents of this register are then parallel

loaded into the serial/parallel register and clocked out of the device by

scl.

At the end of each byte, in both read and write message sequences, an acknowledge is

issued by the receiving device. A positive acknowledge involves holding the SDA line LOW,

a negative acknowledge involves releasing the SDA line to be pulled HIGH. Although the

VT5366 is always considered to be a slave device, it acts as a transmitter when the bus

master requests a read from the sensor.

A message can only be terminated by the bus master, either by issuing a stop condition, a

repeated start condition or by a negative acknowledge after reading a complete byte during

a read operation.

S

address[7:1]

R/W bit

A

DATA[7:0]

A

Sensor acknowledges valid address

Acknowledge from slave

INDEX[7:0]

P

A

A

DATA[7:0]

R/W