M37544G Mitsubishi Electric, M37544G Datasheet - Page 29

• Manufacturer Part Number: M37544G
• Description: Single-Chip 8-Bit CMOS Microcomputer
• Manufacturer: Mitsubishi Electric

A-D Converter
The functional blocks of the A-D converter are described below.
[A-D conversion register] AD
The A-D conversion register is a read-only register that stores the
result of A-D conversion. Do not read out this register during an A-
D conversion.
[A-D control register] ADCON
The A-D control register controls the A-D converter. Bit 2 to 0 are
analog input pin selection bits. Bit 4 is the AD conversion comple-
tion bit. The value of this bit remains at “0” during A-D conversion,
and changes to “1” at completion of A-D conversion.
A-D conversion is started by setting this bit to “0”.
[Comparison voltage generator]
The comparison voltage generator divides the voltage between
AV
[Channel selector]
The channel selector selects one of ports P2
and inputs the voltage to the comparator.
[Comparator and control circuit]
The comparator and control circuit compares an analog input volt-
age with the comparison voltage and stores its result into the A-D
conversion register. When A-D conversion is completed, the con-
trol circuit sets the AD conversion completion bit and the AD
interrupt request bit to “1”. Because the comparator is constructed
linked to a capacitor, set f(X
version.
Fig. 32 Block diagram of A-D converter
SS
and V
REF
Data bus
P2
P2
P2
P2
P2
P2
by 256, and outputs the divided voltages.
0
1
2
3
4
5
/AN
/AN
/AN
/AN
/AN
/AN
A-D control register
0
1
2
3
4
5
(Address 0034
IN
) to 500 kHz or more during A-D con-
16
)
Comparator
3
b7
5
/AN
5
to P2
A-D control circuit
0
/AN
0
,
V
Resistor ladder
REF
A-D conversion register
Fig. 31 Structure of A-D control register
8
b7
V
b0
SS
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
b0
A-D interrupt request
A-D control register
(ADCON : address 0034
Analog input pin selection bits
Disable (returns “0” when read)
AD conversion completion bit
Disable (returns “0” when read)
000 : P2
001 : P2
010 : P2
011 : P2
100 : P2
101 : P2
110 : Disable
111 : Disable
0 : Conversion in progress
1 : Conversion completed
(Address 0035
0
1
2
3
4
5
/AN
/AN
/AN
/AN
/AN
/AN
0
1
2
3
4
5
7544 Group
16
16
, initial value: 10
)
16
)
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