Serial control bus

VT5366

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6.3

Types of messages

This section gives guidelines on the basic operations to read data from and write data to the

serial interface.

The serial interface supports variable length messages. A message may contain no data

bytes, one data byte or many data bytes. This data can be written to or read from common

or different locations within the sensor. The range of instructions available are detailed

below.

–

A write message with no data byte is used to set the index for a subsequent read

message.

–

Multiple location writes may be used for faster information transfers.

Examples of these operations are given below. A full description of the internal registers is

while this bit is set in the read address.

6.3.1

Single location, single data write

When a random value is written to the sensor, the message looks as shown in

Figure 10.

Figure 10.

Single location, single write

In this example, the

zero for writing and the

increment of the index after writing the value. The address index is preserved and may be

used by a subsequent read. The write message is terminated with a stop condition from the

master.

6.3.2

Multiple location write

It is possible to write data bytes to consecutive adjacent internal registers without having to

send explicit indexes prior to sending each data byte. An auto-increment write is

assumed if no stop condition occurs.

Figure 11.

Multiple location write

S

20h

A

0

32h

A

85h

A

P

Start

Device

Ack

address

Index

Data

Stop

SA

11

A

AA

20h

16

C1

Incremental write

P

data written

@ index = 17

data written

@ index = 16