| 摘要 |
PURPOSE:To always eliminate scanning, by forming a matrix with row lines and column lines and applying the same signal to all lines of one side and at the same time detecting signal variations of either one of lines of the other side. CONSTITUTION:A matrix is formed with row lines 1(11-1n) and column lines 2(21-2n), and these lines 1 and 2 are connected to a scan signal generator 5 and a discriminator 8, respectively. An AND gate 6 delivers L when any one of lines 2 is set at L. A latching circuit 7 latches the state of the gate 6 when it is changed to L from H and changes the output to H from L to release the reset state for both the generator 5 and the discriminator 8. The discriminator 8 discriminates the keys which are pushed during scanning with the input of the line 2. The circuit 7 is released when the key scanning is over. Therefore it is sufficient to perform the original scanning only when either one of keys is pushed. Thus the scanning frequency is reduced to minimize the effect of noises. |
