VX6953CB datasheet(66/107 Pages) STMICROELECTRONICS

66 / 107 page

Video timing

VX6953CB

66/107

8209023 Rev 5

6.5.2

Digital gain

To help compensate for the relatively coarse analog gain steps, VX6953CB contains a

digital multiplier to “fill” in the missing steps. By mixing analog and digital gain it is possible

to implement 3% gain steps across the full 1x to 16x gain range.

The details of the digital gain implementation are:

•

four individual 16-bit digital channel gains - one per Bayer channel

–

digital_gain_greenR (0x020E and 0x020F)

–

digital_gain_red (0x0210 and 0x0211)

–

digital_gain_blue (0x0212 and 0x0213)

–

digital_gain_greenB (0x0214 and 0x0215)

•

the digital gain range for each channel is 1.000 to 1.96875 in steps of 0.03125 (1/32)

that is, five fractional bits

–

digital_gain_min {0x1084:0x1085} = 0x0100 (1.00)

–

digital_gain_max {0x1086:0x1087} = 0x01F8 (1.96875)

–

digital_gain_step {0x1088:0x1089} = 0x0008 (0.03125)

6.5.3

Integration and gain parameter retiming

The modification of exposure parameter (coarse, fine, clock division or gain) register values

does not take effect immediately.

The exact time at which changes to certain parameters take effect is controlled both to

ensure that each frame of image data produced has consistent settings and that changes in

groups of related parameters can be synchronized.

A group of parameter changes is marked by the host using a dedicated Boolean control

parameter, grouped_parameter_hold (register 0x0104). Any changes made to “retimed”

parameters while the grouped_parameter_hold signal is in the “hold” state will be

considered part of the same group. Only when the grouped_parameter_hold control signal

is moved back to the default “no-hold” state will the group of changes be executed.

VX6953CB Datasheet(PDF) 66 Page - STMicroelectronics