VS6955CA datasheet(22/90 Pages) STMICROELECTRONICS

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Camera control interface (CCI)

VS6955CA

22/90

DocID028071 Rev 2

Camera control interface (CCI)

This chapter specifies the camera control interface (CCI). The I2C-type interface uses 1.8 V

I/O with two signals: serial data line (SDA) and serial clock line (SCL). CCI is used for

control data transfer. Clock signal (SCL) generation is performed by the master device (the

camera module is a slave device). The master device initiates data transfer. The CCI bus on

the camera module has a maximum speed of 400 Kbits/s and has a software switchable

device address. The default device address is 0x20.

Any internal register that can be written to, can also be read from. There are also read only

registers that contain device status information, for example, design revision details. A read

instruction from an unused register location returns the value 0x00. A read instruction from a

reserved address may return any value. A write instruction to a reserved or unused register

location is illegal and the effect of such a write is undefined. It is the responsibility of the host

system to only write to register locations which have been defined.

4.1

Valid register data types

The contents of the registers can represent a number of different data types (see Table 8).

The register map uses this coding to help with the interpretation of the contents of each

Table 8. Valid register data types

Data type

Name

Range

Description

8UI

8-bit unsigned integer

0 to 255

8SI

8-bit signed integer

-128 to 127

Two’s complement notation

16UI

16-bit unsigned integer 0 to 65535

16SI

16-bit signed integer

-32768 to 32767

Two’s complement notation

16UR

16-bit unsigned iReal

0 to 255.99609375

08.08 fixed point number. 8 integer

bits (MS Byte), 8 fractional bits (LS

Byte)

16SR

16-bit signed iReal

-128 to 127.9960375

Two’s complement notation,

8 fractional bits

32UR

32-bit unsigned iReal

0 to 65535.99998474

16.16 fixed point number.

16 integer bits (MS 2 Bytes),

16 fractional bits (LS 2 Bytes)

32SF

32-bit IEEE floating-

point number

As per IEEE 754

As per IEEE 754. 1 sign bit,

8 exponent bits, 23 fractional bits

8C or 16C 8-bit or 16-bit coded

This indicates that the value is

decoded to select one of several

functions or modes.

8B or 16B

8 or 16 bits

-b

Each bit represents a specific

function or mode.

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