S1C63454 TECHNICAL MANUAL
EPSON
41
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (LCD Driver)
4.7 LCD Driver (COM0–COM16, SEG0–SEG39)
4.7.1 Configuration of LCD driver
The S1C63454 has 17 common terminals (COM0–COM16) and 40 segment terminals (SEG0–SEG39), so
that it can drive a dot matrix type LCD with a maximum of 680 (40
×
17) dots.
The driving method is 1/17 duty, 1/16 duty or 1/8 duty dynamic drive with four voltages (1/4 bias),
V
C1
, V
C2
, V
C4
and V
C5
(1/5 bias driving can be set by impressing five voltages from outside).
LCD display ON/OFF can be controlled by the software.
4.7.2 Power supply for LCD driving
V
C1
–V
C5
are driving voltages for the LCD, and for which either the voltages generated by the LCD
system voltage circuit or voltages to be supplied from outside can be used. The built-in LCD system
voltage circuit generates four voltages (1/4 bias) V
C1
, V
C2
, V
C4
and V
C5
except for V
C3
. These four output
voltages can be supplied to the outside only for driving the externally expanded LCD driver.
When external voltages are supplied, 1/5 bias driving can be made by inputting five voltages to the V
C1
–
V
C5
terminals (including V
C3
).
Either the internal generated voltages or external voltages used for the LCD drive voltage can be selected
by the mask option.
Turning the LCD system voltage circuit ON or OFF is controlled with the LPWR register. This control is
also necessary when supplying the voltage from outside. When LPWR is set to "1", the LCD system
voltage circuit outputs the LCD drive voltages V
C1
–V
C5
to the LCD driver.
When "internal voltage" is selected by the mask option, the LCD system voltage circuit generates V
C1
or
V
C2
with the voltage regulator incorporated in itself, and generates three other voltages by boosting or
reducing the voltage V
C1
or V
C2
. Table 4.7.2.1 shows the V
C1
, V
C2
, V
C4
and V
C5
voltage values and boost/
reduce status.
Table 4.7.2.1 LCD drive voltage when generated internally
LCD drive voltage
V
C1
(0.975–1.2 V)
V
C2
(1.950–2.4 V)
V
C4
(2.925–3.6 V)
V
C5
(3.900–4.8 V)
V
DD
= 1.8–6.4 V
V
C1
(standard)
2
×
V
C1
3
×
V
C1
4
×
V
C1
V
DD
= 2.6–6.4 V
1/2
×
V
C2
V
C2
(standard)
3/2
×
V
C2
2
×
V
C2
Note: The LCD drive voltage can be adjusted by the software (see Section 4.7.6). Values in the table are
typical values.
Select either V
C1
standard or V
C2
standard using the VCCHG register.
When "1" is written to the VCCHG register, V
C2
standard is selected and when "0" is written, V
C1
stan-
dard is selected. At initial reset, V
C1
standard (VCCHG = "0") is set.
