7220 Datasheet, PDF (155/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

M37220M3-XXXSP/FP
4.5 Functional description
4.5.5 D-A converter
M37220M3-XXXSP/FP has 2 D-A converter with 6-bit resolution. Figure 4.5.7 shows the D-A converter
block diagram.
Data bus
DA1 conversion register
6 (address 00DE16)
DA2 conversion register
6 (address 00DF16)
Resistor ladder
Resistor ladder
DA1 output enable bit
DA2 output enable bit
P30/A-D5/DA1
P31/A-D6/DA2
Fig. 4.5.7 D-A converter block diagram
D-A conversion is performed by setting the value in
the DA conversion 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 00CD16).
The output analog voltage V is determined with the
value n (n: decimal number) in the DA conversion
register.
V=VCC ! ⁿ (n= 0 to 63)
64
The DA output does not build in a buffer, so connect
an external buffer when driving a low-impedance
load.
Table 4.5.4 Relationship between contents of D-A conversion
register and output voltage “V”
A-D control register
Output
bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 voltage “V”
0 00000
0/64 VCC
0 00001
1/64 VCC
0 00010
2/64 VCC
: :::::
:
1 11101
61/64 VCC
1 11110
62/64 VCC
1 11111
63/64 VCC
7220 Group User’s Manual
4-17