Patent ID: 8289049

Claim:
A signal level adjustment method for adjusting a level of a signal outputted from a signal output circuit, the method comprising: setting a threshold of a signal input circuit to a first variable value by a control circuit; determining a level of a first signal in said signal output circuit by the control circuit so that a voltage of said first signal, outputted from said signal output circuit and inputted to said signal input circuit, falls into a given range defined based on said threshold, wherein said determining said level of said first signal comprises selecting a value from a plurality of values of level including a number of values which is greater than four, said determining of the level of said first signal being based on a feedback of a received signal from the signal input circuit according to the setting of the threshold for a repeated pattern data sent to the signal output circuit from the control circuit; and repeatedly adjusting the level of the first signal at the signal output circuit according to a comparison of the feedback of the received signal from the signal input circuit and the repeated pattern data sent to the signal output circuit from the control circuit.