ADE3800SXT datasheet(71/138 Pages) STMICROELECTRONICS

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ADE3800

4.13 Gamma (GAM)

The Gamma block implements three independent 256 point gamma curves for each of R, G, and B

channels.

Its features are as follows:

● 256x8b table per color channel stores 2’s complement difference to straight line

● 10b input/output (0 to 1023), range of delta = -128 to +127 (+/- 1/8

th full scale)

● double LUT amplitude control to change range to 2 x (delta = -256 to +254)

● fast write mode for loading 3 tables with the same data

● glitch free write mode

● clipping on output to [0,1023]

● programmable offset_value added from offset_position0 to offset_position1 (inclusive).

gamma_out_r = gamma_in_r + lut_r + (offset_position0 <= gamma_in_r <= offset_position1) ?

offset_value: 0

gamma_out_g = gamma_in_g + lut_g + (offset_position0 <= gamma_in_g <= offset_position1) ?

offset_value: 0

gamma_out_b = gamma_in_b + lut_b + (offset_position0 <= gamma_in_b <= offset_position1) ?

offset_value: 0

Table 28: Gamma Registers

I2C Address Label

Addr

Mode

Bits

Rst

Description

GAM_CTRL

0C00

R/W

[3]

0*: delta range = -128 to +127

1: delta range = -256 to +254

[2]

0*: i2c to RAM transfer at selected i2c address only

1: i2c to RAM transfer the same value to Red, Green, and Blue

RAMs when selecting Red RAM addresses

[1]

0*: Write i2c to RAM allowed during active video

1: Write i2c to RAM during video blanking only (shadowed)

[0]

0*: gamma bypassed

1: gamma enabled

GAM_POSITION0

0C01

R/W

[7:0]

IF (gamma_in/4 >= offset_position0 && gamma_in/4 <=

offset_position1)

THEN offset = offset_value * 16

ELSE offset = 0

(gamma_out = gamma_in + lut + offset)

GAM_POSITION1

0C02

R/W

[7:0]

See offset_position0 for details

GAM_OFFSET

0C03

R/W

[5:0]

Multipled by 16. 2’s complement number represents –512 to

+496 inclusive.

See offset_position0 for details

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