MITSUBISHI MICROCOMPUTERS
3827 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
D-A CONVERTER
The 3827 group has an on-chip D-A converter with 8-bit resolution
and 2 channels (DAi (i=1, 2)). 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. When using the D-A converter,
the corresponding port direction register bit (P56/DA1, P57/DA2)
should be set to “0” (input status).
b7
b0
D-A control register
(DACON : address 003616)
DA1 output enable bit/DA1 VREF
ON/OFF switch
DA2 output enable bit/DA2 VREF
ON/OFF switch
The output analog voltage V is determined by the value n (base
10) in the D-A conversion register as follows:
Not used (return “0” when read)
0 : Output disabled/OFF
1 : Output enabled/ON
V=VREF ✕ n/256 (n=0 to 255)
Where VREF 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 goes to
high impedance state. The DA output is not buffered, so connect
an external buffer when driving a low-impedance load.
Fig. 35 Structure of D-A control register
Data bus
D-A1 conversion register (0034 16
D-A2 conversion register (0035 16
)
)
D-A i conversion register (8)
DA i output enable bit
R-2R resistor ladder
P5
P5
6
/DA
/DA
1
2
7
Fig. 36 Block diagram of D-A converter
Internal: D-A output
External: VREF
Reference voltage input select switch
V
REF
A-D conversion register
Resistor ladder
(10 bits)
V
REF input
ON/OFF switch
D-A1 output enable switch
D-A1 VREF ON/OFF switch
D-A1 output
(P5
6
)
D-A1 conversion register (8 bits)
R-2R resistor ladder
D-A2 output enable switch
D-A2 VREF ON/OFF switch
D-A2 output
(P5
R-2R resistor ladder
D-A2 conversion register (8 bits)
7)
Fig. 37 A-D converter, D-A converter block diagram
34
MITSUBISHI [ Mitsubishi Group ]
