| 摘要 |
<p>PROBLEM TO BE SOLVED: To select a program without the need of a port to be exclusively used for selecting the program and to efficiently use the port by judging a potential impressed to the port and selecting the program corresponding to the judged potential. SOLUTION: A load circuit composed of a light emitting diode 16, a current limiting resistor 17 and a parallel resistor 19 is connected between the port 13 and a reference potential side. Then, a selection signal for selecting a first program 4 or a second program 5 is decided depending on whether the potential impressed to the port 13 is at an 'H' level or an 'L' level at the time of performing an initialization processing. Thus, the potential impressed to the port 12 when the port 13 used as an output port is set to an input port is turned to the selection signal of the programs 4 and 5 and the programs 4 and 5 corresponding to the selection signal are selected.</p> |
