
2.7 LCD drive control circuit
APPLICATION
2–157
3820 GROUP USER’S MANUAL
Table 2.7.2 Pin functions by setting the corresponding registers when they are not used as seg-
ment output pins
Ports
Pins
(1) Segment output pins (SEG
0
–SEG
39
)
Up to 40 segment outputs can be selected. Table 2.7.3 shows setting of segment output pins for LCD
display.
Table 2.7.3 Setting of segment output pins for LCD display
PULLA (Address 0016
16
) b3
(Bit 3 of PULL register A)
1
0
1
0
P1D (Address 0003
16
) b0
(Bit 0 of port P1 direction register)
P0D (Address 0001
16
) b0
(Bit 0 of port P0 direction register)
PULLA (Address 0016
16
) b0
(Bit 0 of PULL register A)
PULLA (Address 0016
16
) b1
(Bit 1 of PULL register A)
Setting
Register
Value
Pin function
Output port
Input port
Output port
Pull-down pin
SEG
0
–SEG
15
Segment output-only pin
P0
0
–P0
7
P1
0
–P1
7
P3
0
–P3
7
Setting
1
0
Input port
Pull-down pin
(When being set for the input mode)
Pull-down pin
(When being set for the input mode)
Ports P3
0
–P3
7
are used as segment signal output pins (SEG
16
–SEG
23
) by setting
bit 0 of the segment output enable register (address 0038
16
) to “1.”
Ports P0
0
and P0
1
are used as segment signal output pins (SEG
24
, SEG
25
) by setting
bit 1 of the segment output enable register (address 0038
16
) to “1.”
Ports P0
2–
P0
7
are used as segment signal output pins (SEG
26
–SEG
31
) by setting
bit 2 of the segment output enable register (address 0038
16
) to “1.”
Ports P1
0
and P1
1
are used as segment signal output pins (SEG
32
, SEG
33
) by setting
bit 3 of the segment output enable register (address 0038
16
) to “1.”
Port P1
2
is used as segment signal output pins (SEG
34
) by setting bit 4 of the segment
output enable register (address 0038
16
) to “1.”
P1
2
/SEG
34
Ports P1
3–
P1
7
are used as segment signal output pins (SEG
35
–SEG
39
) by setting
bit 5 of the segment output enable register (address 0038
16
) to “1.”
P3
0
/SEG
16
–
P3
7
/SEG
23
P0
0
/SEG
24
,
P0
1
/SEG
25
P0
2
/SEG
26
–
P0
7
/SEG
31
P1
0
/SEG
32
,
P1
1
/SEG
33
P1
3
/SEG
35
–
P1
7
/SEG
39
No pull-down
1
0
No pull-down
(When being set for the input mode)
1
0
No pull-down
(When being set for the input mode)