ST7781
1. Gradient Adjustment Registers
The gradient adjustment registers are used to adjust the gradient of the curve representing the relationship between the
grayscale and the grayscale reference voltage level. To adjust the gradient, the resistance values of variable resistors in the
middle oh the ladder resistor are adjusted by registers PRP0[2:0]/PRN0[2:0], PRP1[2:0]/PRN1[2:0]. The registers consist
of positive and negative polarity registers, allowing asymmetric drive.
2. Amplitude Adjustment Registers
The amplitude adjustment registers, VRP0[3:0]/VRN0[3:0], VRP1[4:0], are used to adjust the amplitude of grayscale
voltages. To adjust the amplitude, the resistance values of variable resistors at the top and the bottom of the ladder resister
are adjusted.
3. Fine Adjustment Registers
The fine adjustment registers are used to fine-adjust grayscale voltage levels. To fine-adjust grayscale voltage levels, fine
adjustment registers adjust the reference voltage level, 8 levels for each register generated from the ladder resistor, in
respective 8-to-1 selectors. Same with other registers, the fine adjustment registers consist of positive and negative polarity
registers.
Fig.16.3 Gamma curve adjustment
Register Groups
Positive Polarity
PRP0[2:0]
Negative Polarity
PRN0[2:0]
Description
Variable Resistor VRCP0,VRCN0
Variable Resistor VRCP1,VRCN1
Variable Resistor VROP0,VRON0
Gradient Adjustment
PRP1[2:0]
PRN1[2:0]
VRP0[3:0]
VRN0[3:0]
Amplitude
Adjustment
VRP1[4:0]
KP0[2:0]
KP1[2:0]
KP2[2:0]
KP3[2:0]
KP4[2:0]
KP5[2:0]
VRN1[4:0]
KN0[2:0]
KN1[2:0]
KN2[2:0]
KN3[2:0]
KN4[2:0]
KN5[2:0]
Variable Resistor VROP1,VRON1
8-to-1 Selector (Voltage Level of Grayscale1)
8-to-1 Selector (Voltage Level of Grayscale8)
8-to-1 Selector (Voltage Level of Grayscale20)
8-to-1 Selector (Voltage Level of Grayscale43)
8-to-1 Selector (Voltage Level of Grayscale55)
8-to-1 Selector (Voltage Level of Grayscale62)
Fine Adjustment
Table 16.4: Register Description
Ver. 1.7
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