Technical information
34
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
3822 Group
MITSUBISHI MICROCOMPUTERS
LCD DRIVE CONTROL CIRCUIT
The 3822 group has the built-in Liquid Crystal Display (LCD) drive
control circuit consisting of the following.
●LCD display RAM
●Segment output enable register
●LCD mode register
●Selector
●Timing controller
●Common driver
●Segment driver
●Bias control circuit
A maximum of 32 segment output pins and 4 common output pins
can be used.
Up to 128 pixels can be controlled for LCD display. When the LCD
Fig. 32 Structure of segment output enable register and LCD mode register
enable bit is set to “1” after data is set in the LCD mode register,
the segment output enable register and the LCD display RAM, the
LCD drive control circuit starts reading the display data automati-
cally, performs the bias control and the duty ratio control, and
displays the data on the LCD panel.
Table 11 Maximum number of display pixels at each duty ratio
Duty ratio Maximum number of display pixel
64 dots
or 8 segment LCD 8 digits
96 dots
or 8 segment LCD 12 digits
128 dots
or 8 segment LCD 16 digits
2
3
4
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0
0
3
9
1
6)
Segment output enable register
(SEG : address 0038
16)
Duty ratio selection bits
0 0 : Not used
0 1 : 2 (use COM
0, COM1)
1 0 : 3 (use COM
0–COM2)
1 1 : 4 (use COM
0–COM3)
Bias control bit
0 : 1/3 bias
1 : 1/2 bias
LCD enable bit
0 : LCD OFF
1 : LCD ON
Not used (returns “0” when read)
(Do not write “1” to this bit)
LCD circuit divider division ratio selection bits
0 0 : Clock input
0 1 : 2 division of clock input
1 0 : 4 division of clock input
1 1 : 8 division of clock input
LCDCK count source selection bit (Note)
0 : f(X
CIN)/32
1 : f(X
IN)/8192 (or f(XCIN)/8192 in low-speed
mode)
N
o
t
e
:
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Segment output enable bit 0
0 : Input port P3
4–P37
1 : Segment output SEG12–SEG15
Segment output enable bit 1
0 : I/O port P0
0,P01
1 : Segment output SEG16, SEG17
Segment output enable bit 2
0 : I/O port P0
2–P07
1 : Segment output SEG18–SEG23
Segment output enable bit 3
0 : I/O port P1
0,P11
1 : Segment output SEG24, SEG25
Segment output enable bit 4
0 : I/O port P1
2
1 : Segment output SEG26
Segment output enable bit 5
0 : I/O port P1
3–P17
1 : Segment output SEG27–SEG31
Not used (returns “0” when read)
(Do not write
“1”
to this bit.)
b
7b
0
b
7b
0