| 摘要 |
PURPOSE:To accurately perform A/D conversion irrelevantly to the specification voltage of a microcomputer by connecting a resistance to be inspected where a current to the converted flows to output parts of the microcomputer which have the same characteristics with output ports to which ladder resistances are connected. CONSTITUTION:One-terminal sides of ladder resistances 32R...R for A/D conversion are connected to respective corresponding output ports 12a...12f of the microcomputer 1, and the other-terminal sides are connected in common and grounded through a resistance ra for voltage generation while being connected to a comparator 2. A thermistor 3 which is the resistance to be inspected is also connected to another output port 12g of the microcomputer 1, and this output port 12g is opened and closed by an input control part 11g having the same characteristic as that of input control parts 11a...11f corresponding to the output 12a...12f. Further, the other terminal of the thermistor 3 is grounded through a resistance rb having the same resistance value as that of the resistance ra and also connected to the comparator 2. The output of the comparator 2 is supplied to the microcomputer 1 and the output state when the value varies from 'L' level to 'H' level is regarded as an A/D-converted value.
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