| 摘要 |
PURPOSE:To perform the switch of clocks without causing the variation of the clock width of the switching part by stopping the clock contained in an output with the input of a switch signal and opening a switch circuit by synchro nizing with the next clock. CONSTITUTION:The oscillation circuits 200 and 300 are connected to a clock switch circuit 100 for production of clocks f1 and f2. When a frequency switch signal is applied via a terminal 400, the circuit 100 outputs the clock f1 with the switch signal of 'H' and the clock f2 with the switch signal of 'L' respectively. The circuit 100 contains 1st and 2nd switch means, and the 2nd switch means stops the output of the f2 synchronously with the f2 when the switch signal is supplied during the output of the f2. Then the 1st switch means outputs the f1 synchronously with the f1. When the f2 is outputted during the output of the f1, the 1st switch means works and the 2nd switch means works synchronously with the f2 to output the f2. In such a constitution, the setting operation of an IC card is omitted and therefore the software load is reduced. |
