| 摘要 |
PURPOSE:To prevent the malfunctions of an external edge detecting circuit by using a reset circuit which eliminates an edge detecting signal that is produced by the change of the input signal produced when a port function display signal changes. CONSTITUTION:An external edge detecting circuit contains a reset circuit 30 which supplies an input signal DIN received from a port part and a port function display signal F that changes by the input/output changeover of the port part and detects the change of the signal DIN due to the change of the signal F to produce a reset signal S37. Then an edge detecting circuit is added to input the signal DIN and output it synchronously with a clock signal CLK and to be reset by the signal S37. When both signals DIN and F are supplied to a detecting means, the change of the signal DIN due to the change of the signal F is detected and the signal S37 is produced. |
