3807 Datasheet, PDF (45/75 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3807 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
D-A Converter
The 3807 group has an on-chip D-A converter with 8-bit resolution
and 4 channels (DAi (i=1—4)). The D-A converter is performed by
setting the value in the D-A conversion register. The result of D-A
converter is output from DAi pin by setting the DAi output enable bits
to "1." When using the D-A converter, the corresponding port direc-
tion register bit (P65/DAVREF/AN10, P56/DA1, P57/DA2, P80/DA3/AN11,
P81/DA4/AN12) should be set to "0" (input status).
The output analog voltage V is determined by the value n (base 10)
in the D-A conversion register as follows:
V=DAVREF x n/256 (n=0 to 255)
Where DAVREF is the reference voltage.
At reset, the D-A conversion registers are cleared to "0016", the DAi
output enable bits are cleared to "0", and DAi pin is set to input (high
impedance). The DA output is not buffered, so connect an external
buffer when driving a low-impedance load.
b7
b0
D-A control register
(DACON : address 003316)
DA1 output enable bit
DA2 output enable bit
DA3 output enable bit
DA4 output enable bit
Not used (return "0" when read)
0 : Output disabled
1 : Output enabled
Fig. 44. Structure of D-A control register
Data bus
D-A1 conversion register (003616)
D-A2 conversion register (003716)
D-A3 conversion register (003816)
D-A4 conversion register (003916)
D-A i conversion register (8)
DA i output enable bit
R-2R resistor ladder
P56/DA1
P57/DA2
P80/DA3/AN11
P81/DA4/AN12
Fig. 45. Block diagram of D-A converter
DA i output enable bit (Note)
P56/DA1
"0"
P57/DA2
P80/DA3/AN11
P81/DA4/AN12 ^"1"
R
R
R
R
R
R
2R
2R
2R
2R
2R
2R
MSB
D-A i conversion
register (Note)
"0" "1"
AVSS
P65/DAVREF/AN10
Note: i=1 to 4
R
2R
2R
2R
LSB
Fig. 46. Equivalent connection circuit of D-A converter
44