| 摘要 |
PURPOSE:To execute control irrespective of the number of keys of a key group, and to make a device simple and inexpensive by forming a controlling circuit for controlling a keyboard matrix with discrete parts. CONSTITUTION:When no key of a key group 30 is depressed, an H signal is all inputted to 8-input NAND elements 120, 121, and their output L signals are inputted to a D input of a FF 150 through an OR element 122. That is to say, a Q' output becomes H, a decoding circuit 20 is operated by inputting a reference clock 7 to a counter circuit 13, and a scan of 16 lines of the key group 30 is continued. Subsequently, when A is brought to key-in, one input of the elements 120, 121 becomes L, and their output H signals are inputted to the D input of the FF 150 through the element 122. That is to say, the Q' output becomes L, the circuit 13 stops the clock 7, and the circuit 20 also stops its scan. A CPU reads each information from row and column status registers 14 110 and 111 with respective to this state, and decodes a fact that A has been brought to key-in. |
