475
18.5 LCD Display RAM in the LCD Controller Driver
18.5 LCD Display RAM in the LCD Controller Driver
The LCD display RAM is 14 x 4 bit (7 byte) display data memory for generating
segment output signals.
I
LCD Display RAM and Output Pins
The description in this RAM is read automatically in synch with the selection timing of the
common signal and output from the segment output pins.
If the description in each bit is "1," it is output after being converted into the selected voltage
(LCD is displayed). If the description in each bit is "0," it is output after being converted into the
non-selected voltage (LCD is not displayed).
Since the LCD display operation is performed independently of the CPU operation, the LCD
display RAM can be read and written in any timing.
Of the SEG8 to SEG15 pins, the pins not specified as segment output are used as an I/O port
(general-purpose output) and the corresponding RAM can be used as an ordinary RAM.
Table 18.5-1 "Relationships between Duty and Common Output and the Bits Used in the LCD
Display RAM" shows the relationships between duty and common output and the bits used in
the
LCD display RAM. Figure 18.5-1 "Assignment of the LCD Display RAM and the Common/
Segment Output Pins" shows the assignment of the LCD display RAM and the common/
segment output pins.
Figure 18.5-1 Assignment of the LCD Display RAM and the Common/Segment Output Pins
bit3
bit7
bit3
bit7
bit3
bit7
bit3
bit7
bit3
bit7
bit3
bit7
bit3
bit7
Address
bit2
bit6
bit2
bit6
bit2
bit6
bit2
bit6
bit2
bit6
bit2
bit6
bit2
bit6
bit1
bit5
bit1
bit5
bit1
bit5
bit1
bit5
bit1
bit5
bit1
bit5
bit1
bit5
bit0
bit4
bit0
bit4
bit0
bit4
bit0
bit4
bit0
bit4
bit0
bit4
bit0
bit4
SEG0
SEG1
SEG2
SEG3
SEG4
SEG5
SEG6
SEG7
SEG8
SEG9
SEG10
SEG11
SEG12
SEG13
0060
H
0061
H
0063
H
0064
H
0065
H
0066
H
Area and common pins used at 1/2 duty
Area and common pins used at 1/3 duty
Area and common pins used at 1/4 duty
COM3 COM2 COM1 COM0
0062
H