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
Register
index
Bits Function Default Comment
0x20 0 Fine MSB exposure value 0 Line length dependent
0x21 [7:0] Fine LSB exposure value
0x22 0 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 0 Bits[3:0] IDAC control
0x25 [3:0] Clock divisor value 0
See
[0x25] - Clock divider setting
for details
0x2C [1:0] Dark offsetH 0 Dark offset manual settings
0x2D [7:0] Dark offsetL 0
0x2E [7:0] Dark offset control register 0
