STV0974 datasheet(21/69 Pages) STMICROELECTRONICS

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Functional description

STV0974

21/61

4.5.3

Direct registers

Access to the microprocessor interface direct registers is controlled by the state of CSN, RDN,

WRN and RS (

Table 8).

The direct registers are used to access all STV0974 indirect registers and external image sensor

registers through I²C. To read from a camera register:

1 Write AR with the indirect register address.

2 Poll the status register RDY bit until high.

3 Read the register data from DR.

To write to a camera register:

1 Write AR with the indirect register address.

2 Write DW with the register data.

3 Poll the status register RDY bit until high.

Note: 1 16-bit values are in little-endian representation, i.e. LSB at lower address.

2 No data polling is required to access the microprocessor interface indirect registers.

Address Register (AR)

The Address Register holds the 16-bit address of the camera register to access. AR is written by

two consecutive byte writes, least significant byte first.

Note:

To avoid LSB/MSB sequence mismatch, any read access (to DR or SR) guarantees that the

following write to AR updates the LSB (ADDR bits 7:0).

Table 8: Microprocessor Interface Direct Registers

CSN

RDN

WRN

Address Register (AR)

Status Register (SR)

Data Write register (DW)

Data Read register (DR)

No access

Table 9: Address Register

Bits

Name

Type

Description

0 = Image sensor register (forward command to I²C master).

STV0974 register.

0 = Write access

1 = Read access

[13:0]

ADDR

Camera register address.

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