VV6501 datasheet(38/60 Pages) STMICROELECTRONICS

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I2C Registers

VV6501

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5.2.3

Exposure control registers

There is a set of programmable registers which control the sensor sensitivity. The registers are as

follows:

Fine exposure

Coarse exposure time

Analogue gain

Clock division

The gain parameter does not affect the integration period rather it amplifies the video signal at the

output stage of the sensor core.

Note:

The external exposure (coarse, fine, clock division or gain) values do not take effect immediately.

Data from the serial interface is read by the exposure algorithm at the start of a video frame. If the

user reads an exposure value via the serial interface, then the value reported will be the data as yet

unconsumed by the exposure algorithm, because the serial interface logic locally stores all the data

written to the sensor.

Between the writing the of exposure data and the use of the data by the exposure logic, bit 0 of the

status register is set. The gain value is updated a frame later than the coarse, fine and clock division

parameters, since the gain is applied directly at the video output stage and does not require the long

set up time of the coarse, fine exposure and of the clock division.

To eliminate the possibility of the sensor array seeing only part of the new exposure and gain

settings, if the serial interface communication extends over a frame boundary, the internal re-timing

of exposure and gain data is disabled while writing data to any location in the exposure page of the

serial interface register map. Thus if the 5 bytes of exposure and gain data is sent as an auto-

increment sequence, it is not possible for the sensor to consume only part of the new exposure and

gain data.

The range of some parameter values is limited and any value programmed out of the range is

clipped to the maximum allowed.

Table 12: Exposure, clock rate and gain registers

index

Bits

Function

Default

Comment

0x20

Fine MSB exposure value

Line length dependent

0x21

[7:0]

Fine LSB exposure value

0x22

Coarse MSB exposure value

0x20A

Frame length dependent.

Maximum for default modes:

VGA = 522

0x23

[7:0]

Coarse LSB exposure value

0x24

[7:0]

Analogue gain value

Bits[3:0] IDAC control

0x25

[3:0]

Clock divisor value

See

[0x25] - Clock divider setting

for details

0x2C

[1:0]

Dark offsetH

Dark offset manual settings

0x2D

[7:0]

Dark offsetL

0x2E

[7:0]

Dark offset control register

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