| 摘要 |
PURPOSE:To simplify a circuit, by arraying a shift key and switches on the same matrix as normal keys. CONSTITUTION:When a power supply is connected to a one-chip microprocessor and its program starts to run, I/O port terminals P25 P20 are changed so that each scan line is turned to low at its voltage successively one by one. In every switching of each scan line 49 to the low mode, the microprocessor 46 reads out the status of a return line connected to a bus line, detects a key depressed in accordance with the status and generates the key code to store the key code its internal buffer. Since lines 50, 51 to which the shift key and switches are set up is scanned in the same manner, the microprocessor 46 can always supervise the depressed status of the shift key and switches. |
