| 摘要 |
<p>PROBLEM TO BE SOLVED: To conduct a clock switching without hazard. SOLUTION: This clock switching circuit corresponding to hot plug includes the first FF group 43 which takes in switching off signal of cable CLKSEL in response to the first clock, and the second FF group 45 which takes in switching off signal of cable CLKSEL in response to the second clock. In the first FF group, when a cable is disconnected the final step of FF takes the first selected signal out in response to several steps of clock edges. When a cable is connected, the final step of FF outputs the first unselected signal in response to one time of clock edge. The first FF group selects and outputs the first clock in response to the first selected signal, and prohibits outputting the first clock in response to the first unselected signal. In the second FF group, when a cable is connected, the final step of FF outputs the second selected signal in response to several steps of clock edges. When a cable is disconnected, the final step of FF outputs the second unselected signal in response to one time of clock edge. The second FF group selects and outputs the second clock in response to the second selected signal, and prohibits outputting the second clock in response to the second unselected signal. According to the relation the frequency of the first clock and the second one, the first FF group has more steps than the second FF group.</p> |
