HT45F3420 Datasheet, PDF (110/141 Pages) Holtek Semiconductor Inc – Personal Care Flash MCU

HT45F3420/HT45F3430
Personal Care Flash MCU
LCD SCOM Function – only for HT45F3430
The HT45F3430 device has the capability of driving external LCD panels. The common pins for
LCD driving, SCOM0~SCOM3, are pin shared with certain pin on the I/O ports. The LCD signals
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.
The LCD driver function is controlled using the SCOMC 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 VDD/2 voltage levels for LCD 1/2 bias operation.
The SCOMEN bit in the SCOMC 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.
V _DD
S C O M o p e r a tin g c u r r e n t
V _{D D} /2
S C O M 0~S C O M 3
P in - s h a r e d s e le c tio n b its
SCO M EN
LCD COM Bias
LCD Bias Current Control
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 resistor choice is implemented using the ISEL1 and
ISEL0 bits in the SCOMC register.
SCOMC Register
Bit
7
6
5
4
3
2
1
0
Name
─
ISEL1 ISEL0 SCOMEN ─
─
─
─
R/W
─
R/W
R/W
R/W
─
─
─
─
POR
─
0
0
0
─
─
─
─
Bit 7
Bit 6~5
Bit 4
Bit 3~0
Unimplemented, read as "0"
ISEL1~ISEL0: Select resistor for R type LCD bias current (VDD=5V)
00: 2×100kΩ (1/2 Bias), IBIAS=25μA
01: 2×50 kΩ (1/2 Bias), IBIAS=50μA
10: 2×25 kΩ (1/2 Bias), IBIAS=100μA
11: 2×12.5 kΩ (1/2 Bias), IBIAS=200μA
SCOMEN: LCD function enable control bit
0: Disable
1: Enable
When SCOMEN is set, it will turn on the DC path of resistor to generate 1/2 VDD bias voltage.
Unimplemented, read as "0"
Rev. 1.31
110
April 11, 2017