VT5366V032 datasheet(18/30 Pages) STMICROELECTRONICS

18 / 30 page

Serial control bus

VT5366

18/30

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.

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

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. Its begins with a

start condition and ends with either

stop condition or another start condition In this situation the (second) start is referred to as

repeated start and is shown as (Sr). The first byte of a transaction always contains the

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

read

or 0 write. Thus the 8 bit device address for the VT5366 is 0x20 for writing and 0x21 for

reading.

Figure 8.

VT5366 serial interface address

Start condition

Stop condition

SDA

SCL

Acknowledge

Address or data byte

MSB

LSB

R/W

VT5366V032 Scheda tecnica(PDF) 18 Page - STMicroelectronics

VT5366V032 Scheda tecnica(HTML) 18 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Scheda tecnica Scarica

Link URL