M37221 Mitsubishi, M37221 Datasheet - Page 34

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

34
D-A CONVERTER
The M37221EF-XXXSP has 2 D-A converters with 6-bit resolution.
D-A converter block diagram is shown in Figure 34.
D-A conversion is performed by setting the value in the DA conver-
sion register. The result of D-A conversion is output from the DA pin
by setting “1” to the DA output enable bit of the port P3 output mode
control register (bits 2 and 3 at address 00CD
The output analog voltage V is determined with the value n (n: deci-
mal number) in the DA conversion register.
The DA output does not build in a buffer, so connect an external
buffer when driving a low-impedance load.
Fig. 32. Structure of D-A converter register
Fig. 34. D-A converter block diagram
7
V = V
0
CC
64
n
(n = 0 to 63)
0
DA conversion set bits
Fix this bit to “0.”
DA1 conversion register
(DA1: address 00DE
DA2 conversion register
(DA2: address 00DF
Refer to Table 8.
DA1 conversion register
16
).
Resistor ladder
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
P3
0
/A-D5/DA1
6
(address 00DE
16
16
DA1 output enable bit
)
)
Data bus
16
M37221EF-XXXSP,M37221EFSP
)
Table 8. Relation between contents of D-A conversion register and
Fig. 33. Structure of port P3 output mode register
Bit 5
0
0
0
1
1
1
7
DA2 conversion register
Resistor ladder
P3
output voltage
Bit 4
0
0
0
1
1
1
D-A conversion register
1
/A-D6/DA2
6
with ON-SCREEN DISPLAY CONTROLLER
(address 00DF
Bit 3
DA2 output enable bit
0
0
0
1
1
1
MITSUBISHI MICROCOMPUTERS
Bit 2
0
0
0
1
1
1
0
16
)
Bit 1
P3
P3
DA1 output enable bit
DA2 output enable bit
Port P3 output mode control
register
(P3S: address 00CD
0
0
1
0
1
1
0 : CMOS output
1 : N-channel open-drain output
0 : CMOS output
1 : N-channel open-drain output
0 : P3
1 : DA1 output
0 : P3
1 : DA2 output
0
1
output structure selection bit
output structure selection bit
0
1
Bit 0
input/output
input/output
0
1
0
1
0
1
voltage “V”
61/64 V
62/64 V
0/64 V
1/64 V
2/64 V
16
63/64V
Output
)
CC
CC
CC
CC
CC
CC