Clock generating apparatus, test apparatus and clock generating method

A test apparatus for testing a device under test, comprising:

• a clock generating apparatus that generates a recovered clock by recovering an edge of a received signal received from the device under test, the clock generating apparatus including:
• a recovered clock generating section that generates the recovered clock;
• a multi-strobe generating section that generates a plurality of strobes with different phases, in accordance with a pulse of the recovered clock;
• a detecting section that detects a position of an edge of the received signal relative to the strobes, by referring to values of the received signal obtained at respective timings of the strobes;
• an adjusting section that adjusts a phase of the recovered clock, in accordance with the position of the edge of the received signal, by shifting the phase of the recovered clock by a time corresponding to a difference between (i) a position of one of the strobes that detects the position of the edge of the received signal and (ii) a position of a predetermined boundary strobe selected from among the strobes;
• and
• a storage section that stores therein a reference time amount by which the adjusting section shifts the phase of the recovered clock, wherein
• the test apparatus further comprises:
• a receiving section that receives at least one of the received signal and a parallel signal transmitted from the device under test in parallel with the received signal, in accordance with the recovered clock;
• and
• a judging section that judges whether the signal received by the receiving section is acceptable,
• the adjusting section is operable to shift the phase of the recovered clock by the reference time amount in such a manner that the position of the boundary strobe approaches the position of the edge of the received signal,
• if a predetermined reference difference is exceeded by the difference between (i) the position of the strobe that detects the position of the edge of the received signal and (ii) the position of the predetermined boundary strobe, then the adjusting section shifts the phase of the recovered clock by the time corresponding to the difference, and
• if the predetermined reference difference is not exceeded by the difference between (i) and (ii), then the adjusting section shifts the phase of the recovered clock by the reference time amount in such a manner that the position of the boundary strobe approaches the position of the edge of the received signal.

A clock generating method performed by a clock generating apparatus for generating a recovered clock by recovering a clock from an edge of a received signal, the clock generating method comprising:

• generating the recovered clock by a recovered clock generating section of the clock generating apparatus;
• generating, by a multi-strobe generating section of the clock generating apparatus, a plurality of strobes with different phases, in accordance with a pulse of the recovered clock;
• detecting, by a detecting section of the clock generating apparatus, a position of an edge of the received signal relative to the strobes, by referring to values of the received signal at respective timings of the strobes;
• adjusting, by an adjusting section of the clock generating apparatus, a phase of the recovered clock in accordance with the position of the edge of the received signal, by shifting the phase of the recovered clock by a time corresponding to a difference between a position of one of the strobes that detects the position of the edge of the received signal and a position of a predetermined boundary strobe selected from among the strobes;
• and
• storing, in a storage section of the clock generating apparatus, a reference time amount by which the phase of the recovered clock is shifted, wherein
• if a predetermined reference difference is exceeded by the difference between (i) the position of the strobe that detects the position of the edge of the received signal and (ii) the position of the predetermined boundary strobe, then the phase of the recovered clock is shifted by the time corresponding to the difference, and
• if the predetermined reference difference is not exceeded by the difference between (i) and (ii), then the phase of the recovered clock is shifted by the reference time amount in such a manner that the position of the boundary strobe approaches the position of the edge of the received signal.