Serial control bus

VT5366

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6

Serial control bus

6.1

General description

The 2-wire I2C serial interface bus is used to read and write the VT5366 registers.

The main features of the serial interface include:

–

Variable length read/write messages

–

Indexed addressing of information source or destination within the sensor

–

Automatic update of the index after a read or write message

–

Message abort with negative acknowledge from the master

–

Byte oriented messages

6.2

Serial communication protocol

The co-processor must perform the role of communication ‘master’ and the sensor acts as a

‘slave’. The communication from host to sensor takes the form of 8-bit data with a maximum

serial clock frequency of 400 kHz. Since the serial clock is generated by the bus master it

determines the data transfer rate. Data transfer protocol on the bus is illustrated in

Figure 7.

Figure 7.

Serial Interface data transfer protocol

6.2.1

Data format

Information is packed in 8-bit packets (bytes) always followed by an acknowledge bit. The

internal data is produced by sampling

stable during the high period of

when

A message contains at least two bytes. Its begins with a

a

a

device address byte in the upper 7 bits with the LSB indicating the data direction; 1 for

read

reading.

Figure 8.

VT5366 serial interface address

12

7

8

A

Start condition

Stop condition

SDA

SCL

Acknowledge

P

S

3

4

56

Address or data byte

MSB

LSB

0

0

1

0

0

0

0

R/W