M38197MA Datasheet, PDF (31/60 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3819 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Data bus
b7
AD-DA control register
(address 002C16)
4
P70/AN0
P71/AN1
P72/AN2
P73/AN3
P74/AN4
P75/AN5
P76/AN6
P77/AN7
P50/SIN2/AN8
P51/Sout2/AN9
P52/SCLK2 /AN10
P53/SRDY2 /AN11
P54/SIN3 /AN12
P55/SOUT3 /AN13
P56/SCLK3 /AN14
P57/SRDY3 /AN15
Comparator
Fig. JA-2 A-D converter block diagram
b0
A-D control circuit
A-D conversion register
(Address 002D16)
8
Resistor ladder
VREF
AVSS
A-D conversion interrupt request
D-A CONVERTER
The 3819 group has internal D-A converter with 8-bit resolutions !
1 channel.
D-A conversion is performed by setting the value in the D-A con-
version register. The result of D-A conversion is output from the
DA pin by setting the DA output enable bit to “1” . At this time, the
corresponding bit (PB2/DA) of the port PB direction register should
be set to “0” (input status).
The output analog voltage V is determined with the value n
(n: decimal number) in the D-A conversion register as follows:
V=VREF ! n/256 (n=0 to 255)
VVREF: the reference voltage
At reset, the D-A conversion register is cleared to “0016”, the DA
output enable bits are cleared to “0”, and the PB2/DA pin goes to
high impedance state. The D-A output does not build in a buffer, so
connect an external buffer when driving a low-impedance load.
Set VCC to 3.0 V or more when using the D-A converter.
D-A conversion register (8)
R-2R resistor ladder
DA output enable bit
PB2/DA
Fig. JB-1 D-A converter block diagram
PB2/DA
"0" DA output enable bit _R
"1"
2R
MSB
D-A conversion
register
"0" "1"
AVSS
VREF
R
2R
R
2R
R
2R
R
2R
R
2R
R
2R
2R
2R
LSB
Fig. JB-2 Equivalent connection circuit of D-A converter
31