Patent ID: 7714629

Claim:
A delay circuit for adjusting a delay time of signal propagation of wiring of a wiring board, said delay circuit comprising: an interface for giving a command of setting a delay time; a delay device that can be set to any desired delay time; and a storage device for storing a parameter for defining a delay time, wherein said delay device is adapted to have a delay time set based on the parameter according to the command from said interface and said delay device is adapted to be provided at both an input end and an output end of the wiring of the wiring board, and wherein said delay device has: a signal generator for transmitting a propagation time measuring signal to the wiring of the wiring board to set the delay time in a measurement mode; a reception section for receiving the propagation time measuring signal reflected on the wiring of the wiring board to set the delay time in the measurement mode; a measurement section for measuring the time difference between the time at which the reception section receives the propagation time measuring signal and the time at which the signal generator transmits the propagation time measuring signal and setting the half time of the time difference as a signal propagation time about the wiring of the wiring board to set the delay time in the measurement mode; and a determination section for determining that the time difference between the maximum one of the signal propagation times measured about the wiring of the wiring board and the signal propagation time measured about the wiring of the wiring board to set the delay time is the delay time of the wiring of the wiring board to set the delay time.