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Rev. 1.21
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HT66F488/HT66F489
A/D Flash MCU with EEPROM
HT66F488/HT66F489
A/D Flash MCU with EEPROM
Software LCD Driver
The devices have the capability of driving external LCD panels. The common pins for LCD driving,
SCOM0~SCOM5, and segment pins, SSEG0~SSEG29, are pin shared with certain pin on the I/O
ports. The LCD signals (COM and SEG) are generated using the application program.
LCD operation
An external LCD panel can be driven using this device by configuring the I/O pins as common
pins and configuring the I/O pins as segment pins. The LCD driver function is controlled using the
S
LCDC0~SLCDC4 registers which in addition to controlling the overall on/off function, LCD bias
current setup function also controls the pin function selection. This enables the LCD COM and SEG
driver to generate the necessary V
SS
, (1/3)V
DD
, (2/3)V
DD
voltage and V
DD
levels for LCD 1/3 bias
operation.
The LCDEN bit in the SLCDC0 register is the overall master control for the LCD driver. The
LCD SCOMn pin is selected to be used for LCD driving by the corresponding pin-shared function
selection bits. Note that the Port Control register does not need to first setup the pins as outputs to
enable the LCD driver operation.
VDD
VSS
LCD
Voltage
Select
Circuit
Analog
Switch
VDD
SCOM0
SCOM5
SSEG0
SSEG29
VSS
V
DD
(2/3)V
DD
(1/3)V
DD
VSS
LCD Driver structure
LCD Control Registers
The LCD COM driver enables a range of selections to be provided to suit the requirement of the
LCD panel which are being used. The bias current choice is implemented using the ISEL1 and
ISEL0 bits in the SLCDC0 register, the FRAME bit is used to select the output frame.