HD404328 Datasheet, PDF (66/96 Pages) Hitachi Semiconductor – 4 BIT SINGLE CHIP MICROCOMPUTER

HD404328 Series
LCD Output Register (LOR: $015): Write-only register used to specify that ports R2–R5 act as pins
SEG1–SEG16, as shown in table 32.
Table 32 LCD Output Register
LOR
Bit 3 Port Selection
0
R5
1
SEG16–SEG13
LOR
LOR
Bit2 Port Selection Bit 1 Port Selection
0
R4
0
R3
1
SEG12–SEG9 1
SEG8–SEG5
LOR
Bit 0 Port Selection
0
R2
1
SEG4–SEG1
Large Liquid-Crystal Panel Drive and V_LCD: To drive a large-capacity LCD, decrease the resistance of
the built-in division resistors by attaching external resistors in parallel, as shown in figure 40.
Since HD404328U and HD4074329U do not have built-in division resistors, they require external LCD
voltage division resistors for voltage adjustment.
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—and 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
kΩ to 10 kΩ would usually be suitable. (Another effective method is to attach capacitors of 0.1 µF 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).
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