Test apparatus and test method
A time measurement unit measures the time interval between edges to be monitored in a signal under test DUT_Output including serial data output from a device under test (DUT) 400 . A comparison judgment unit calculates the number of bits of the serial data included between the edges to be monitored, based on the time interval thus measured. Furthermore, the comparison judgment unit compares the number of bits thus calculated with an expected value thereof.
1. A test apparatus comprising:
a time measurement unit operable to measure a plurality of time intervals in a signal under test, wherein the signal under test includes a plurality of edges and the plurality of edges include a plurality of monitored edges, wherein respective time intervals in the plurality of time intervals correspond to respective measurements of time between the monitored edges, wherein the signal under test includes serial data output from a device under test; and
a comparison judgment unit operable to calculate a number of bits in of the serial data output included between the monitored edges, based on the respective time intervals in the plurality of time intervals included in the signal under test, and to compare the number of bits with an expected number of bits value to generate a comparison result.
2. The test apparatus according to claim 1 , wherein the time measurement unit is operable to generate a respective time stamp T[i] for each of the monitored edges, and wherein the comparison judgment unit is operable to round off a quotient obtained by dividing respective edge intervals interval represented by ΔTi=T[i+1]−T[i] by an ideal unit interval to generate a calculation result, and to employ the calculation result as the number of bits of the serial data output, wherein the respective edge intervals correspond to the respective time intervals between the monitored edges.
3. The test apparatus according to claim 2 , wherein
the time measurement unit comprises:
a data decimation unit operable to select the monitored edges of the signal under test for each N of the plurality of edges, wherein N represents a first integer; and
a time stamper operable to assign the time stamp to the monitored edges extracted by the data decimation unit.
4. The test apparatus according to claim 3 , wherein the data decimation unit comprises a polarity selector operable to select at least one of a positive edge or a negative edge from the signal under test.
5. The test apparatus according to claim 3 , wherein the data decimation unit comprises:
a pre-scaler operable to select respective edges for each K of the plurality of edges, wherein K represents a second integer; and
an inter-discarder arranged on a downstream stage from the pre-scaler, and operable to select respective edges extract for each L of the plurality of edges, wherein L represents a third integer.
6. The test apparatus according to claim 1 , wherein the comparison judgment unit is mounted in a DSP (Digital Signal Processor).
7. The test apparatus according to claim 1 , wherein the comparison judgment unit is operable to generate a pass/fail signal that corresponds to the comparison result.
8. The test apparatus according to claim 7 , wherein a value of the pass/fail signal indicates a pass if the comparison result is a match.
9. The test apparatus according to claim 7 , wherein a value of the pass/fail signal indicates a fail if the comparison result is not a match.
10. A test method for a signal under test including serial data output from a device under test, the test method comprising:
measuring a plurality of time intervals in a signal under test, wherein the signal under test includes a plurality of edges and the plurality of edges include a plurality of monitored edges, wherein respective time intervals included in the plurality of time intervals correspond to respective measurements of time between respective monitored edges included in the plurality of monitored edges, wherein the signal under test includes serial data output from a device under test;
calculating a number of bits of the serial data output included between the respective monitored edges, based on the respective time intervals in the plurality of time intervals; and
comparing the number of bits that is calculated with an expected value to generate a comparison result.
11. The test method according to claim 10 , wherein respective ones of the plurality of monitored edges are selected for each N of the plurality of edges, and wherein the test method is executed with respective i-th edge of the plurality of edges, an (i+N)-th edge of the plurality of edges, (i+2×N)-th edge of the plurality of edges, . . . , as the monitored edges, while incrementing i from 1 to N.
12. The test method according to claim 10 , wherein a monitored edge is extracted for each N of the plurality of edges, wherein N is an odd number, and wherein the test method is executed with predetermined edge numbers of the plurality of edges while repeatedly inputting the signal under test comprising an even number of the plurality of edges for each pattern period in a plurality of pattern periods.
13. The test method according to claim 10 , further comprising: generating a pass/fail signal that corresponds to the comparison result.
14. The test method according to claim 13 , wherein a value of the pass/fail signal indicates a pass if the comparison result is a match.
15. The test method according to claim 13 , wherein a value of the pass/fail signal indicates a fail if the comparison result is not a match.
16. A test apparatus comprising:
a time measurement unit operable to measure a plurality of time intervals in a signal under test, wherein the signal under test includes a plurality of edges and the plurality of edges include a plurality of monitored edges, wherein respective time intervals in the plurality of time intervals correspond to respective measurements of time between the monitored edges, wherein the signal under test includes serial data output from a device under test;
a comparison judgment unit operable to calculate a number of bits of the serial data output included between the monitored edges based on the respective time intervals in the plurality of time intervals, and to compare the number of bits with an expected value to generate a comparison result; and
a jitter remover operable to remove jitter from the signal under test by rounding the number of bits to an integer value.
17. The test apparatus according to claim 16 , wherein the comparison judgment unit is operable to generate a pass/fail signal that corresponds to the comparison result.
18. The test apparatus according to claim 17 , wherein the time measurement unit is operable to generate respective time stamps for the monitored edges.
19. The test apparatus according to claim 18 , wherein the time measurement unit comprises:
a data decimation unit operable to select the monitored edges of the signal under test for each N of the plurality of edges, wherein N represents a first integer; and
a time stamper operable to assign the respective time stamps to the monitored edges, wherein the monitored edges are selected by the data decimation unit.
20. The test apparatus according to claim 19 , wherein the data decimation unit comprises a polarity selector operable to select at least one of a positive edge or a negative edge from the signal under test.