| 摘要 |
PURPOSE:To obtain a required control signal without increasing the number of terminals of an LSI by providing a cycle counter circuit to detect the cycle of the level change of a control input signal, and a selection circuit to select a level, the one depending on the cycle counter circuit or a control input signal level, based on whether or not the continuance of the level change of the control input signal. CONSTITUTION:The title control circuit is constituted of a level change detection circuit 37, the cycle counter circuit 39, and the selection circuit 40. A reset signal 25 and a control switching signal 26 are synchronized with an input clock signal, and are inputted alternately to the control circuit at an interval set in advance. The input level change detection circuit 37 detects the level change of the control input signal 15 between the reset signal 25 and the control switching signal 26. The cycle counter circuit 30 is operated so as to obtain a count value corresponding to the level change. In such a way, the count values corresponding to the cycles of the level change can be obtained as first control signals (33-35). The selection circuit 40 selects the control signal depending on the count value set in advance when the level change between the reset signal 25 and the control switching signal 26 continues, and selects the control input signal when no level change continues, then, outputs it as a second control signal 36. |
