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Rev. 1.40
104
March 29, 2019
Rev. 1.40
105
March 29, 2019
HT45F23A/HT45F24A
TinyPower
TM
Flash MCU with OPA & Comparators
HT45F23A/HT45F24A
TinyPower
TM
Flash MCU with OPA & Comparators
SCOM Function for LCD
The devices have the capability of driving external LCD panels. The common pins for LCD driving,
SCOM0~SCOM3, are pin shared with certain pin on the PA0, PC4~PC6 pins. 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 PA0 and PC4~PC6 pins
as common pins and using other output ports lines as segment pins. The LCD driver function is
controlled using the LCDC register which in addition to controlling the overall on/off function also
controls the bias voltage setup function. This enables the LCD COM driver to generate the necessary
V
DD
/2 voltage levels for LCD 1/2 bias operation.
The LCDEN bit in the LCDC register is the overall master control for the LCD driver, however this
bit is used in conjunction with the COMnEN bits to select which I/O pins are used for LCD driving.
Note that the Port Control register does not need to first setup the pins as outputs to enable the LCD
driver operation.
The following block diagram illustrates the functional structure for LCD COM function.
LCDBUF
LCDBUF Disable
LCDEN
COMnEN
SCOM0 ~ SCOM3
Buffer
ISEL
LCD SCOM
Output Current
Generator
10uA
25uA
LCDBUF Enable
LCD Circuit
LCDEN
COMnEN
Pin Function
Output Level
0
X
I/O
High or Low
1
0
I/O
High or Low
1
1
SCOMn
VM
Output Control
LCD Bias Control
The LCD COM driver enables two kinds of selection to be provided to suit the requirement of the
LCD panel which is being used. The bias resistor choice is implemented using the ISEL bit in the
LCDC register.