
Rev.3.01
REJ03B0158-0301
Aug 08, 2007
Page 129 of 134
38D5 Group
Notes on LCD Drive Control Circuit
1. Multiplier Circuit
When the multiplier circuit is used, set the multiplier circuit
control bit to “1” (multiplier circuit enabled) after applying a
voltage from 1.3 V or more to 2.1 V or less to the V
L1
pin.
When the multiplier circuit is not used, set the V
L3
connection bit
to “1” (open) and apply an appropriate voltage to the LCD power
source input pins (V
L1
to V
L3
). When the V
L3
connection bit is
set open, the V
L3
pin is placed in the high impedance state.
When the multiplier circuit is used, set the LCDCK frequency to
100 Hz or more. The on-chip oscillator cannot be used as
LCDCK.
In a system where the multiplier circuit is used (a multiplier
capacitor is externally connected between the C
1
and C
2
pins),
set the multiplier circuit control bit to “1” (multiplier circuit
enabled) before executing the STP or WIT instruction.
2. Setting Data to LCD Display RAM
To write data to the LCD display RAM when the LCD enable bit
is set to “1” and while LCD is turned on, set fixed data.
Rewriting with temporary data may cause LCD to flicker. The
following shows a processing example to write data to the LCD
display RAM while LCD is turned on.
Fig. 105 Processing example when writing data to LCD display RAM While LCD Turned On
(1) Ccorrect processing
LCD
on
LCD
on or
off
*Content at address 0840
16
: “FF
16
”
Off
On
Set LCD display RAM data
LRAM0 (address 0840
16
)
←
“FF
16
”
LCD on or off
Set LCD display RAM data
LRAM0 (address 0840
16
)
←
“00
16
”
Set fixed data to LCD display RAM
(2) Incorrect processing
LCD
on
LCD
on or
off
*Content at address 0840
16
: “FF
16
”
Off
On
Set LCD display RAM data
LRAM0 (address 0840
16
)
←
“FF
16
”
LCD on or off
Set LCD display RAM data
LRAM0 (address 0840
16
)
←
“00
16
”
Set off data to LCD display RAM
LCD
off
Set fixed data to LCD display RAM