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21.3.5 Panel power ON/OFF sequence
Some panels use several power supplies, and these supplies and interface logic signals must be turn on or off in
sequences specified by the manufacturers. The LCD controller has signals to control these power supplies.
Each power supply is controlled via the VPBIAS or VPLCD pin. These pins are connected to a pull-up or pull-down
resistor in addition to the power supply. When the power is off, these pins are placed into high impedance, so that the
resistor pulls the power supply on/off input to the off state.
The power-on/off sequence is started by setting the PowerC bit of the PWRCONREG2 register. Setting this bit to 1
starts the power-on sequence. In the power-on sequence the power supply control pins are brought out of high
impedance to a programmed state at a programmed time, and the panel interface signals become active at a
programmed time. The following table lists the control pins and the programming register bits.
For example, storing 1 in the BiasCon bit and 3 in the Biason field brings the LCD controller to make the VPBIAS
signal from high impedance to high level three frames after the PowerC bit is set to 1, not counting the frame in which
the PowerC bit is changed.
Setting the PowerC bit to 0 starts the power-off sequence. In the power-off sequence the control pins are put into
high impedance, so that the power supply is turned off. The pins enter high impedance in the reverse order of the
power-on sequence, but the time delay between the two control pins remains the same.
CHAPTER 21 LCD CONTROLLER
Pin
Power-on time bit
VPBIAS
Biason(4:0)
VPLCD
Vccon(4:0)
LCD Interface
I/Fon(4:0)
User's Manual U14272EJ3V0UM
Power-on state bit
BiasCon
VccC
− (active)
407
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