VV6501 datasheet(28/60 Pages) STMICROELECTRONICS

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Serial Control Bus

VV6501

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Serial Control Bus

4.1

General description

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

Some status registers are read-only.

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.

4.2

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 100 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 22.

4.2.1

Data format

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

data is produced by sampling

sda at a rising edge of scl. The external data must be stable during

the high period of

scl. Exceptions to this are start (S) or stop (P) conditions when sda falls or rises

respectively, while

scl is high.

A message contains at least two bytes preceded by a

start condition and followed by either a stop or

repeated start, (Sr) followed by another message.

Figure 22: Serial Interface data transfer protocol

Start condition

Stop condition

SDA

SCL

Acknowledge

Address or data byte

MSB

LSB

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