M38197MA Datasheet, PDF (30/60 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3819 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
A-D CONVERTER
The functional blocks of the A-D converter are described below.
A-D Conversion Register (AD) 002D16
The A-D conversion register is a read-only register that stores the
result of an A-D conversion. This register should not be read dur-
ing A-D conversion.
AD/DA Control Register (ADCON) 002C16
The AD/DA control register controls the A-D and the D-A conver-
sion process. Bits 0 to 3 of this register select analog input pins.
Bit 4 is the AD conversion completion bit. The value of this bit re-
mains at “0” during an A-D conversion, then changes to “1” when
the A-D conversion is completed.
The A-D conversion starts by writing “0” to this bit. Bit 6 controls
the output of D-A converter.
Comparison Voltage Generator
The comparison voltage generator divides the voltage between
AVSS and VREF by 256, and outputs the divided voltages.
Channel Selector
The channel selector selects one of the input ports P77/AN7–P70/
AN0, P57/SRDY3/AN15–P50/SIN2/AN8, and inputs to the compara-
tor.
Comparator and Control Circuit
The comparator and control circuit compares an analog input volt-
age with the comparison voltage and stores the result in the A-D
conversion register. When an A-D conversion is completed, the
control circuit sets the AD conversion completion bit and the AD
conversion interrupt request bit to “1”.
Note that the comparator is constructed linked to a capacitor, so
set f(XIN) to 500 kHz or more during A-D conversion.
Note : When using the A-D conversion interrupt, set the INT4/AD conver-
sion interrupt switch bit (the bit 5 of the interrupt selection register)
to “1”.
b7
b0
AD/DA control register
(ADCON : address 002C16)
Analog input pin selection bits
b3 b2 b1 b0
0 0 0 0 : P70/AN0
0 0 0 1 : P71/AN1
0 0 1 0 : P72/AN2
0 0 1 1 : P73/AN3
0 1 0 0 : P74/AN4
0 1 0 1 : P75/AN5
0 1 1 0 : P76/AN6
0 1 1 1 : P77/AN7
1 0 0 0 : P50/SIN2/AN8
1 0 0 1 : P51/SOUT2 /AN9
1 0 1 0 : P52/SCLK2/AN10
1 0 1 1 : P53/SRDY2 /AN11
1 1 0 0 : P54/SIN3/AN12
1 1 0 1 : P55/SOUT3 /AN13
1 1 1 0 : P56/SCLK3/AN14
1 1 1 1 : P57/SRDY3 /AN15
AD conversion completion bit
0 : Conversion in progress
1 : Conversion completed
Not used (returns “0” when read)
DA output enable bit
0 : Disable
1 : Enable
Not used (returns “0” when read)
Fig. JA-1 Structure of A-D control register
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