I-116
EPSON
S1C88348/317/316/308 TECHNICAL HARDWARE
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (LCD Controller)
5.12 LCD Controller
5.12.1 Configuration of LCD controller
The S1C88xx has a built-in dot matrix LCD driver.
The S1C88348/317/316 allows an LCD panel with a
maximum of 1,632 dots (51 segments
× 32 com-
mons). In the S1C88308 a maximum of 1,312 dots
(41 segments
× 32 commons) are permitted. It also
has an LCD controller for an external LCD driver.
Figure 5.12.1.1 shows the configuration of the LCD
controller and the drive power supply.
5.12.2 Mask option
Selection of the drive duty for the built-in LCD
driver can be selected whether it will be 1/32 and
1/16 software-switched or fixed at 1/8 by the mask
option.
LCD drive duty
s
s 1/32 & 1/16 duty
s
s 1/8 duty
When "1/32 & 1/16 duty" is selected, the drive
duty can be selected by software. When "0" is
written to the drive duty selection register LDUTY,
1/32 duty is selected and when "1" is written, 1/16
duty is selected.
When "1/8 duty" is selected, the drive duty is fixed
at 1/8 and setting of LDUTY becomes invalid.
When the built-in LCD driver is not used, select the
default setting of "1/32 & 1/16 duty".
5.12.3 LCD power supply
For the LCD system drive voltages VC1–VC5, either
the internal power supply or external power supply
can be selected by the mask option.
When the internal power supply is selected, voltage
is generated by the internal voltage regulator and
voltage booster circuits. The internal power supply
can generate two types of reference voltage; TYPE
A (4.5 V) and TYPE B (5.5 V), and either one can be
selected by the mask option.
When external power supply is selected, the
voltage should be supplied from outside of the IC.
LCD power supply
s
TYPE A (4.5 V)
s
s Internal power supply
TYPE B (5.5 V)
s
s External power supply
The internal power supply is designed for a small
scale LCD panel and is not suitable for driving a
panel that has large size pixels or for driving a large
capacity panel using an external expanded LCD
driver. In this case, select external power supply
and input the regulated voltage from outside of the
IC.
Figure 5.12.3.1 shows the circuit examples when
using an external power supply.
Fig. 5.12.1.1 Configuration of LCD controller and drive power supply
Note: A load resistance
between terminals
VSS–VC1 is needed
when driving an LCD
panel that constitutes
a heavy load.
Fig. 5.12.3.1
Circuit examples when using
an external power supply
*
VSS level or high
impedance when
LCD is not
driven.
VC5
VC4
VC3
VC2
VC1
Rxx
VSS
VIN
VC5
VC4
VC3
VC2
VC1
VSS
VIN *
CL (R25)
FR (R26)
VC1
VC2
VC3
VC4
VC5
CA
CB
CC
CD
CE
LCD system
voltage booster
VSS
LCD system
voltage regulater
To expanded
LCD driver
Output port
R25, R26
LCD synchronous
signal generator
CL
FR
LCD contrast
adjustment circuit
LCCLK
LCFRM
LC3
LC2
LC1
LC0
LCD driver
DTFNT
VC3–VC5
LCDC1
LCDC0
LDUTY
Display memory
DSPAR
VC1,
VC2
COM0–COM15
COM16–COM31/SEG66–SEG51
SEG0–SEG50
COM0–COM15
COM16–COM31/SEG56–SEG41
SEG0–SEG40
S1C88348/317/316
S1C88308
(
)