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ML63611 User's Manual
Chapter 16 A/D Converter (ADC)
16.3.1 RC Oscillation Circuit
The A/D converter of the RC oscillation method performs A/D conversion by digitizing the oscillation frequency
ratio of a reference resistance (or capacitance) to a resistance sensor, such as thermistor sensor (or capacitance
sensor).
By taking the ratio of oscillation frequencies of the reference to the sensor, it is possible to A/D convert the
characteristics of a sensor itself by canceling error factors intrinsic to the RC oscillation circuit. Consequently, it is
necessary to oscillate the reference side and the sensor side with the same oscillation circuit and a pair of the
reference side and the sensor side is usually used.
Table 16-1 shows the oscillation mode by Bits 3 to 0 (OM3 to OM0) of the A/D converter control register
(ADCON1). Figures 16-2 to 16-5 show the layout and values of the OM3 to OM0 bits.
ADCON1
Mode
No.
OM3
OM2
0
0
0
1
0
0
2
0
0
3
0
0
4
0
1
5
0
1
6
0
1
7
0
1
8
1
—
Note:
Z: High-impedance output
1/0, 0/1: Active output
—: Arbitrary
OPTION A (C): 1.5 V (3.0 V), Without regulator
circuit for LCD bias
Table 16-1 Oscillation Mode by OM3 to OM0 Bits
CROSC0 output pins
OM1
OM0
RS0
0
0
Z
0
1
1/0
1
0
Z
1
1
Z
0
0
1/0
0
1
Z
1
0
Z
1
1
Z
—
—
Z
RT0
CRT0
CS0
Z
Z
Z
Z
Z
0/1
1/0
Z
0/1
Z
1/0
0/1
Z
0/1
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
16 – 4
OPTION B (D): 1.5 V (3.0 V), With regulator
CROSC1
output pins
Mode
RS1
RT1
IN0 external clock
Z
Z
input mode
RS0-CS0
Z
Z
oscillation
RT0-CS0
Z
Z
oscillation
RT
-CS0
0-1
Z
Z
oscillation
RS0-CT0
Z
Z
oscillation
RS1-CS1
1/0
Z
oscillation
RT1-CS1
Z
1/0
oscillation
IN1 external clock
Z
Z
input mode
Z
Z
(unavailable)
circuit for LCD bias
CROSC0
oscillation
mode
CROSC1
oscillation
mode
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