Fujitsu F2 MC-8FX Family, Hardware Manual

Page: 452 / 602

438
CHAPTER 24 LCD CONTROLLER
■
Use of External Divider Resistors
As the V1 pin is connected to V
SS
(GND) internally via a transistor, when using external divider
resistors, you can shut off the current flowing to the resistors when the LCD controller is halted by
connecting the V
SS
end of the divider resistors to the V1 pin. Figure 24.2-6 shows the states with
external divider resistors used.
Figure 24.2-6 States with External Divider Resistors Used
1) To connect the external divider resistors without being affected by the internal divider resistors,
you need to write "0" to the drive voltage control bit in the LCDC control register
(LCDCC:VSEL) to disconnect all the internal divider resistors. Write "1" to the V3 to V1 select
bits in LCDC enable register 1 (LCDCE1:VE1) so that the target ports can be used as power
supply pins to drive the LCD.
2) When the internal divider resistors are disconnected, writing a value other than "00
B
" to the
display mode select bits (MS1 and MS0) in the LCDC control register turns on the LCDC
enable transistor (Q1) and current flows in the external divider resistors.
3) Writing "00
B
" to the display mode select bits (MS1 and MS0) turns off the LCDC enable
transistor (Q1) and this stops the current flow in the external divider resistors.
Note:
The externally connected RX resistors depend on the LCD you are using. Select appropriate
resistances to match the LCD.
2R
R
R
R
LCDC enabled
Q1
V
3
V
2
V
1
Vcc
V3
V2
V1
VR
RX
RX
RX
V
1
to V
3
: Voltages at V1 to V3 pins