CMI/NRZ CONVERSION CIRCUIT

PROBLEM TO BE SOLVED: To compose a CMI/NRZ conversion circuit of a digital circuit without using a phase locked loop circuit by converting a holding signal holding from the changing point of CMI(code mark inversion) code data at a middle point to the next middle point to NRZ(non-return to zero) code data with the period of a transfer clock. SOLUTION: A falling detection part 1, counter 2 and a decoder 3 constituting a middle point detecting circuit detect the middle point of transferring clocks generated from CMI code data to detect the changing point of CMI code data at this detected middle point. A flip-flop 4 as a holding signal generating circuit generates a holding signal from this data changing point to a point before the next middle point. A flip-flop 6 as a conversion circuit receives a holding circuit from the flip-flop 4 and converts it to NRZ code data with the period of a transferring clock to output. Then a CMI/NRZ conversion circuit is realized by the digital circuit.