Fractional frequency divider circuit and data transmission apparatus using the same
First Claim
1. A fractional frequency divider circuit comprising an integer frequency divider circuit and a logic circuit, said integer frequency divider circuit being constituted by multiple master-slave flip-flops, said integer frequency divider circuit frequency-dividing a clock signal with a frequency-division ratio of 1/N where N is an integer, said logic circuit receiving a plurality of signals outputted from master stages and slave stages of said master-slave flip-flops, and outputting a signal with a duty ratio of 50% obtained by frequency-dividing said clock signal with a frequency-division ratio of 2/N.
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Accused Products
Abstract
A fractional frequency divider circuit with a small circuit scale that outputs a clock with a duty ratio of 50%, and a data transmission apparatus comprising same. The fractional frequency divider circuit is constituted by multiple master-slave flip-flops, and comprises an integer frequency divider circuit that frequency-divides a clock signal with a frequency-division ratio of 1/N(N is an integer), and a logic circuit into which multiple signals outputted from master stages and slave stages of the master-slave flip-flops are inputted and that outputs a signal with a duty ratio of 50% obtained by frequency-dividing the clock signal with a frequency-division ratio of 2/N. The data transmission apparatus is constituted such that it is possible to switch over between a frequency-multiplied clock outputted by a PLL and a clock obtained by frequency-dividing the frequency-multiplied clock with the fractional frequency divider circuit for each channel.
47 Citations
12 Claims
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1. A fractional frequency divider circuit comprising an integer frequency divider circuit and a logic circuit, said integer frequency divider circuit being constituted by multiple master-slave flip-flops,
said integer frequency divider circuit frequency-dividing a clock signal with a frequency-division ratio of 1/N where N is an integer, said logic circuit receiving a plurality of signals outputted from master stages and slave stages of said master-slave flip-flops, and outputting a signal with a duty ratio of 50% obtained by frequency-dividing said clock signal with a frequency-division ratio of 2/N.
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3. A data transmission apparatus comprising:
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a receiver circuit that performs serial-parallel conversion on a received signal and outputs the result, a transmitter circuit that performs parallel-serial conversion on a transmitted signal and outputs the result, a PLL that multiplies a reference clock signal and outputs a multiplied clock signal, and a fractional frequency divider circuit that outputs a signal obtained by frequency-dividing said multiplied clock signal with a frequency-division ratio of 2/N where N is an integer, wherein said fractional frequency divider circuit comprises an integer frequency divider circuit and a logic circuit, said integer frequency divider circuit being constituted by multiple master-slave flip flops, said integer frequency divider circuit frequency-dividing said multiplied clock signal with a frequency-division ratio of 1/N, said logic circuit receiving a plurality of signals outputted from master stages and slave stages of said master-slave flip-flops, and outputting a signal obtained by frequency-dividing said multiplied clock signal with a frequency-division ratio of 2/N where N is an integer, and said receiver circuit and transmitter circuit being constituted such that they operate selectively switching over between said multiplied clock signal and a clock signal outputted by said fractional frequency divider circuit. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification