48
EPSON
S1C63656 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (LCD Driver)
4.7 LCD Driver (COM0–COM3, SEG0–SEG37)
4.7.1 Configuration of LCD driver
The S1C63656 has four common terminals (COM0–COM3) and 38 segment terminals (SEG0–SEG37), so
that it can drive an LCD with a maximum of 152 (38
×
4) segments.
The driving method is 1/4 duty or 1/3 duty dynamic drive with three voltages (1/3 bias), V
C1
, V
C2
and
V
C3
.
LCD display on/off can be controlled by the software.
4.7.2 Power supply for LCD driving
The power supply for driving LCD can be selected from the internal power supply and an external power
supply.
When the internal power supply is selected, the LCD drive voltages V
C1
–V
C3
are generated by the built-in
LCD system voltage circuit. The LCD system voltage circuit is turned on and off using the LPWR register.
When LPWR is set to "1", the LCD system voltage circuit outputs the LCD drive voltages V
C1
–V
C3
to the
LCD driver. The LCD system voltage circuit generates V
C1
with the voltage regulator built-in, and
generates two other voltages (V
C2
= 2V
C1
, V
C3
= 3V
C1
) by boosting V
C1
.
When using an external power supply, select the voltage from the following 3 types and supply the LCD
drive voltage to the V
C1
–V
C3
terminals.
1) External power supply 1/3 bias (for 4.5 V panel) V
DD
= V
C2
2) External power supply 1/3 bias (for 3.0 V panel) V
DD
= V
C3
3) External power supply 1/2 bias (for 3.0 V panel) V
DD
= V
C3
, V
C1
= V
C2
(static drive function is available)
Note that the power control using the LPWR register is necessary even if an external power supply is
used. SEG output ports that are set for DC output by the mask option operate same as the output (R) port
regardless of the power on/off control by the LPWR register.
4.7.3 Control of LCD display and drive waveform
(1) Display on/off control
The S1C63656 incorporates the ALON and ALOFF registers to blink display. When "1" is written to
ALON, all the segments go on, and when "1" is written to ALOFF, all the segments go off. At such a
time, an on waveform or an off waveform is output from SEG terminals. When "0" is written to these
registers, normal display is performed. Furthermore, when "1" is written to both of the ALON and
ALOFF, ALON (all on) has priority over the ALOFF (all off).
(2) Setting of drive duty
In the S1C63656, the drive duty can be set to 1/4 or 1/3 using the LDUTY1 and LDUTY0 registers as
shown in Table 4.7.3.1.
Table 4.7.3.1 LCD drive duty setting
LDUTY1
1
1
0
0
LDUTY0
1
0
1
0
Drive duty
1/3
–
–
1/4
Common terminal used
COM0–COM2
–
–
COM0–COM3
Maximum segment number
114 (38
×
3)
–
–
152 (38
×
4)
Table 4.7.3.2 shows the frame frequency corresponding to the drive duty.
Table 4.7.3.2 Frame frequency
OSC1 oscillation frequency
32.768 kHz
When 1/3 duty is selected
42.7
Hz
When 1/4 duty is selected
32
Hz
Figures 4.7.3.1 and 4.7.3.2 show the dynamic drive waveform according to the duty.
