HD404849 Datasheet, PDF (103/125 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404849 Series
LCD output register 3 (LOR3: $01F)
Bit
Initial value
Read/Write
Bit name
3
2
—
0
—
W
Not used LOR32
1
0
0
—
W
—
LOR31 Not used
LOR32
0
1
R7/SEG17–SEG20 mode selection
R7
SEG17–SEG20
LOR31
0
1
R6/SEG13–SEG16 mode selection
R6
SEG13–SEG16
Figure 88 LCD Output Register 3 (LOR3)
Large Liquid-Crystal Panel Drive and V_LCD: If the capacitance of the LCD is very large while being
driven, decrease the capacitance by attaching external resistors in parallel, as shown in figure 89.
The size of these resistors cannot be simply calculated from the LCD load capacitance because the matrix
configuration of the LCD complicates the paths of charge/discharge currents flowing through the
capacitors—the resistance will also vary with lighting conditions. This size must be determined by trial-
and-error, taking into account the power dissipation of the device using the LCD, but a resistance of 1 to 10
kΩ is usually suitable. (Another effective method is to attach capacitors of 0.1 to 0.3 µF.)
Always turn off the power switch (set bit 1 of the LCR to 0) before changing the liquid-crystal drive
voltage (V_LCD).
103