M37221 Mitsubishi, M37221 Datasheet - Page 33

• Manufacturer Part Number: M37221
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER with ON-SCREEN DISPLAY CONTROLLER
• Manufacturer: Mitsubishi

A-D COMPARATOR
A-D comparator consists of 6-bit D-A converter and comparator. A-D
comparator block diagram is shown in Figure 31.
The reference voltage “V
the A-D control register 2 (address 00EF
The comparison result of the analog input voltage and the reference
voltage “V
00EE
For A-D comparison, set “0” to corresponding bits of the direction
register to use ports as analog input pins. Write the data for select of
analog input pins to bits 0 to 2 of the A-D control register 1 and write
the digital value corresponding to V
to 5 of the A-D control register 2. The voltage comparison starts by
writing to the A-D control register 2, and it is completed after 16 ma-
chine cycles (NOP instruction
Fig. 29. Structure of A-D control register 1
Fig. 31. A-D comparator block diagram
7
P0
P1
P3
P3
16
5
6
).
0
1
/INT2/A-D4
/A-D1/INT3
/A-D5/DA1
/A-D6/DA2
P1
P1
ref
6
7
” is stored in bit 4 of the A-D control register 1 (address
/A-D2
/A-D3
A-D control register 1
Bits 0 to 2
Analog
switch
signal
ref
” for D-A conversion is set by bits 0 to 5 of
0
8).
Analog input pin selection bits
Storage bit of comparison result
A-D control register 1
(AD1: address 00EE
0 : Input voltage < reference voltage
1 : Input voltage > reference voltage
b2 b1 b0
0
0
0
0
1
1
1
1
ref
0
0
1
1
0
0
1
1
to be compared to the bits 0
Comparator control
16
0 : A-D1
1 : A-D2
0 : A-D3
1 : A-D4
0 : A-D5
1 : A-D6
0 :
1 :
).
Compa-
rator
Do not set.
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
16
)
Data bus
Bit 4
A-D control
register 1
M37221EF-XXXSP,M37221EFSP
Fig.30. Structure of A-D control register 2
Table 7. Relation between contents of A-D control register 2 and
Bit 5
Bit 5
0
0
0
1
1
1
7
reference voltage “V
Bit 4
0
0
0
1
1
1
A-D control register 2
Bit 4
with ON-SCREEN DISPLAY CONTROLLER
Bit 3
0
0
0
1
1
1
Bit 3
Resistor ladder
Bit 2
0
0
0
1
1
1
Switch tree
A-D control
register 2
ref
”
Bit 1
0
0
0
1
0
1
1
Bit 2
D-A converter set bits
A-D control register 2
(AD2: address 00EF
Bit 0
Refer to Table 7.
0
1
0
1
0
1
Bit 1
123/128 V
125/128 V
127/128 V
voltage “V
Reference
1/128 V
3/128 V
5/128 V
Bit 0
CC
CC
CC
CC
CC
CC
16
ref
)
”
33