Patent ID: 7397878

Claim:
A semiconductor device comprising: a first circuit which recognizes transition in at least one level of a first signal of M bits (M being 3 or larger) based on a clock signal and outputs a second signal of M bits; and a second circuit which receives said second signal and outputs a third signal of N bits (N being 2 or larger), wherein M is larger than N, said first signal is a signal in which transition takes place in at least one level of a predetermined number of signals out of said first signals synchronously with said clock signal, said first signal shifts a level based on a first binary logic value out of M bits synchronously with said clock signal and which maintains the level based on a second logic value at the same level, and said first signal is input from the outside of said semiconductor device, and wherein said first circuit comprises: a plurality of first MOSFETs connected in parallel which receive said first signal of M bits, and each said first MOSFET having a conductance characteristic substantially equal to a first value; a plurality of second MOSFETs connected in parallel, the number of second MOSFETs being M, M−1 said second MOSFETs each having a conductance characteristic substantially equal to said first value, and a remaining second MOSFET has a conductance characteristic which is substantially equal to one half the first value; and a circuit which detects a difference between a first current flowing in said first MOSFETs and a second current flowing in said second MOSFETs and generates a detection signal indicative of validity/invalidity of the first signal, wherein a voltage corresponding to one of two levels of said first signal is supplied to gates of said first MOSFETs which correspond to the number of bits having said first binary logic value, including the remaining second MOSFET, and a voltage corresponding to the other level of the first signal is supplied to the gates of the remaining MOSFETs.