CLUCK SIGNAL SELECTING APPARATUS OF DOUBLE CLUCK SYSTEM

摘要

The clock signal selecting device for a double clock system comprises: a first synchronizing unit for generating a first synchronizing signal which is synchronized with a first clock signal in response to a clock selection signal and stopping generation of the first synchronizing signal in response to a first clear signal; a second synchronizing unit for generating a second synchronizing signal which is synchronized with a second clock signal in response to the clock selection signal and stopping generation of the second synchronizing signal in response to a second clear signal; a first control unit for synchronizing and shifting continuously input logic "1" values with the first clock signal, NANDing the shifted bit value and the clock selection signal and generating the second clear signal; a second control unit for synchronizing and shifting continuously input logic "1" values with the second clock signal, NANDing the shifted bit value and an inverted clock selection signal and generating the first clear signal; and a logic unit for synchronizing the shifted bit values of the first and second control units with the first and second clock signals and logic-operating them.