| 摘要 |
PURPOSE:To make it possible to set a convenient A/D converter with a high degree of accuracy with the use of a control CPU in a vehicle electronic control device, by counting a time from a time point when the CPU delivers an initiation signal to an integrating amplifier to a time point when a comparator issues an output. CONSTITUTION:A CPU3 starts its internal count from a time when its port output becomes a low level, and receives an interrupt signal. The count is stopped at the time when the signal is present so that the output Va of a comparator IC2 becomes a count stop signal, and further, a high level is issued from the outlet port to energize a transistor TR1. Then, the CPU issues the result of the count which is displayed on a display unit, and controls another section to complete its operation. Since the low level section period of the outlet port Vc of the CPU3 is cyclically repeated, measurement may be made always. That is, if the voltage of a battery is low, the output Va becomes a high level at a higher rate so that the number of count is smaller, but if it is higher, the number of counter is large, and therefore, the battery voltage may be digitally counted. |
