| 摘要 |
PROBLEM TO BE SOLVED: To provide a keystroke circuit which can detect a plurality of keystrokes, without using I/O port of a CPU. SOLUTION: This keystroke circuit 1 is provided with a plurality of key switches SWs, bus switches 12 for detecting wire-connected corresponding rows and columns of the key switches SWs, a CPU 11 connected to the bus switches 12 for detecting via a data bus 14, while an interrupt terminal IRQ is connected to the rows and the columns of the key switches SWs, and is connected to the CPU via an address bus 15 and a decoder 13, which outputs select signals which opens the data bus 14 between the CPU 11 and the bus switches 12 for detecting, based on the instructions from the CPU 11. The CPU 11 opens the data buss 14, by outputting the buss opening instruction to the decoder 13, when the interruption signal from the key switches SWs is input to the interruption terminal IRQ, and decides the location of the pushed key switch SW by detecting the operation signal of the key switch SW. COPYRIGHT: (C)2004,JPO&NCIPI
|
