M38503MXH Datasheet, PDF (31/86 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3850 Group (Spec. H)
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
A-D CONVERTER
[A-D Conversion Registers (ADL, ADH)]
003516, 003616
The A-D conversion registers are read-only registers that store the
result of an A-D conversion. Do not read these registers during an
A-D conversion.
[AD Control Register (ADCON)] 003416
The AD control register controls the A-D conversion process. Bits
0 to 2 select a specific analog input pin. Bit 4 indicates 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.
Comparison Voltage Generator
The comparison voltage generator divides the voltage between
AVSS and VREF into 1024 and outputs the divided voltages.
Channel Selector
The channel selector selects one of ports P30/AN0 to P34/AN4 and
inputs the voltage to the comparator.
Comparator and Control Circuit
The comparator and control circuit compare an analog input volt-
age with the comparison voltage, and the result is stored in the
A-D conversion registers. When an A-D conversion is completed,
the control circuit sets the A-D conversion completion bit and the
A-D interrupt request bit to “1”.
Note that because the comparator consists of a capacitor cou-
pling, set f(XIN) to 500 kHz or more during an A-D conversion.
When the A-D converter is operated at low-speed mode, f(XIN)
and f(XCIN) do not have the lower limit of frequency, because of
the A-D converter has a built-in self-oscillation circuit.
b7
b0
AD control register
(ADCON : address 003416)
Analog input pin selection bits
b2 b1 b0
0 0 0: P30/AN0
0 0 1: P31/AN1
0 1 0: P32/AN2
0 1 1: P33/AN3
1 0 0: P34/AN4
Not used (returns “0” when read)
A-D conversion completion bit
0: Conversion in progress
1: Conversion completed
Not used (returns “0” when read)
Fig. 31 Structure of AD control register
10-bit reading
(Read address 003616 before 003516)
b7
b0
(Address 003616)
b9 b8
b7
b0
(Address 003516) b7 b6 b5 b4 b3 b2 b1 b0
Note : The high-order 6 bits of address 003616 become “0”
at reading.
8-bit reading (Read only address 003516)
b7
b0
(Address 003516) _{b9 b8 b7 b6 b5 b4 b3 b2}
Fig. 32 Structure of A-D conversion registers
AD control register
(Address 003416)
P30/AN0
P31/AN1
P32/AN2
P33/AN3
P34/AN4
Data bus
b7
b0
3
A-D control circuit
A-D interrupt request
Comparator
A-D conversion high-order register (Address 003616)
A-D conversion low-order register ^{(Address 003516)}
10
Resistor ladder
Fig. 33 Block diagram of A-D converter
VREF AVSS
31