54
EPSON
S1C63358 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (LCD Driver)
4.8 LCD Driver (COM0–COM3, SEG0–SEG31)
4.8.1 Configuration of LCD driver
The S1C63358 has 4 common terminals (COM0–COM3) and 32 segment terminals (SEG0–SEG31), so that
it can drive an LCD with a maximum of 128 (32
×
4) segments.
The driving method is 1/4 duty, 1/3 duty or 1/2 duty dynamic drive with four voltages (1/3 bias), V
SS
,
V
C1
, V
C2
and V
C3
. It is also possible to set static drive. The drive duty and static drive can be selected by
software. In addition, drive waveform with three voltages (1/2 bias) of V
SS
, V
C1
= V
C2
and V
C3
can be
selected by mask option.
4.8.2 Power supply for LCD driving
The LCD drive voltage V
C1
is generated by the LCD system regulated voltage circuit, and V
C2
and V
C3
are generated by boosting the V
C1
voltage with the LCD system voltage booster circuit.
To generate V
C1
, the supply voltage V
DD
should be 1.4 V or more.
When V
DD
is less than 1.4 V, the LCD display contrast will become worse.
The LCD system voltage circuit that generates V
C1
–V
C3
is turned ON and OFF by the LCD power control
register LPWR.
By setting LPWR to "1", the LCD system voltage circuit generates V
C1
–V
C3
. When LPWR is set to "0",
V
C1
–V
C3
becomes V
SS
level. In this case, all outputs from the COM terminals and SEG terminals go to V
SS
level.
To display the LCD, the LCD drive power must be ON by previously setting LPWR to "1".
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.
4.8.3 Control of LCD display and drive waveform
(1) Display ON/OFF control
The S1C63358 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 S1C63358, the drive duty can be set to 1/4, 1/3 or 1/2 by the software. This setting is done
using the LDUTY1 and LDUTY0 registers as shown in Table 4.8.3.1.
Table 4.8.3.1 LCD drive duty setting
LDUTY1
1
0
0
LDUTY0
∗
1
0
Drive duty
1/2
1/3
1/4
Common terminal used
COM0, COM1
COM0–COM2
COM0–COM3
Maximum segment number
64 (32
×
2)
96 (32
×
3)
128 (32
×
4)
Frame frequency
∗
32 Hz
42.7 Hz
32 Hz
∗
When f
OSC1
= 32.768 kHz
Figures 4.8.3.1 to 4.8.3.6 show the dynamic drive waveform according to the drive bias and duty.
