M38027E8SP Datasheet, PDF (26/51 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3802 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]
The A-D conversion register is a read-only register that stores the
result of an A-D conversion. When reading this register during an
A-D conversion, the previous conversion result is read.
[AD/DA control register]
The AD/DA control register controls the A-D conversion process.
Bits 0 to 2 select a specific analog input pin. Bit 3 signals the
completion of an A-D conversion. The value of this bit remains at
“0” during an A-D conversion, and changes to “1” when an A-D
conversion ends. Writing “0” to this bit starts the A-D conversion.
Bits 6 and 7 are used to control the output of the D-A converter.
[Comparison voltage generator]
The comparison voltage generator divides the voltage between
AVSS and VREF into 256, and outputs the divided voltages.
[Channel selector]
The channel selector selects one of the ports P60/AN0 to P67/AN7,
and inputs the voltage to the comparator.
[Comparator and Control circuit]
The comparator and control circuit compares an analog input volt-
age with the comparison voltage, then stores the result in the A-D
conversion register. When an A-D conversion is complete, the
control circuit sets the AD conversion completion bit and the AD
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 an A-D conversion.
b7
b0
AD/DA control register
(ADCON : address 003416)
Analog input pin selection bits
b2 b1 b0
0 0 0: P60/AN0
0 0 1: P61/AN1
0 1 0: P62/AN2
0 1 1: P63/AN3
1 0 0: P64/AN4
1 0 1: P65/AN5
1 1 0: P66/AN6
1 1 1: P67/AN7
AD conversion completion bit
0: Conversion in progress
1: Conversion completed
Not used (return "0" When read)
DA1 output enable bit
0: DA1 output disabled
1: DA1 output enabled
DA2 output enable bit
0: DA2 output disabled
1: DA2 output enabled
Fig.22 Structure of AD/DA control register
Data bus
AD/DA control register
b7
b0
(Address 0034 16)
P60/AN0
P61/AN1
P62/AN2
P63/AN3
P64/AN4
P65/AN5
P66/AN6
P67/AN7
Fig. 23 Block diagram of A-D converter
3
A-D control circuit
A-D interrupt request
Comparator
A-D conversion register (Address 0035 16)
8
Resistor ladder
VREF AVSS
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