Abstract: A clock switch circuit includes a frequency divide circuit which divides a frequency of a basic clock to generate a plurality of frequency-divided clocks, an output select signal generation circuit which outputs an output select signal according to a clock select signal, and an output select circuit which switches a clock to be output according to the output select signal, in which the frequency divide circuit outputs a plurality of frequency-divided count values indicating the number of clocks of the basic clock from start of one cycle of each of the frequency-divided clocks, and the output select signal generation circuit switches a value of the output select signal at timings at which start timings of cycles of frequency-divided clocks before and after switch operation are matched based on a frequency-divided count value corresponding to a current selection clock among the plurality of frequency-divided count values.

Abstract: A clock switch circuit includes a frequency divide circuit which divides a frequency of a basic clock to generate a plurality of frequency-divided clocks, an output select signal generation circuit which outputs an output select signal according to a clock select signal, and an output select circuit which switches a clock to be output according to the output select signal, in which the frequency divide circuit outputs a plurality of frequency-divided count values indicating the number of clocks of the basic clock from start of one cycle of each of the frequency-divided clocks, and the output select signal generation circuit switches a value of the output select signal at timings at which start timings of cycles of frequency-divided clocks before and after switch operation are matched based on a frequency-divided count value corresponding to a current selection clock among the plurality of frequency-divided count values.

Abstract: In an ATM device comprising a switch core 11, a port shaping unit 25 is arranged within the switch core 11 to carry out a port shaping operation. The port shaping unit 25 controls reading timing of each cell stored in a shared buffer 10. Therefore, a delay to absorb the CDV is decided by the reading timing and the port shaping operation is achieved within the ATM device without attaching any additional memories to the ATM device.