SYNCHRONIZING MEASUREMENT DEVICES USING TRIGGER SIGNALS

• US 20070273419A1
• Filed: 05/22/2007
• Published: 11/29/2007
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: National Instruments Corporation (Emerson Electric Company)
• Original Assignee: National Instruments Corporation (Emerson Electric Company)
• Inventors: Conway, Craig
• Granted Patent: US 7,624,294 B2
• Time in Patent Office: Days
• US Class Current: 327/161
• CPC Class Codes: G01R 19/2516 Modular arrangements for computer based systems; using personal computers (PC's), e.g. "virtual instruments"
• CPC Class Codes: G01R 31/31907 Modular tester, e.g. controlling and coordinating instruments in a bus based architecture

Abstract

Trigger reception on different instrumentation devices may be synchronized by each instrumentation device generating one or more trigger enable signals and delaying performance of an operation in response to a trigger signal until a transition in a trigger enable signal. An instrumentation system may include several instrumentation devices and a communication medium coupling the instrumentation devices. One of the instrumentation devices may process data in response to a sample clock signal. That instrumentation device may also generate a trigger enable signal and delay performing an operation in response to a trigger signal transmitted via the communication medium until a transition in the trigger enable signal occurs. The trigger enable signal is not the sample clock signal. The trigger enable signal may be synchronized to another trigger enable signal generated by another one of the instrumentation devices.

Claims

1. A method comprising:

receiving at both a first and a second instrumentation device a common reference clock;

the first instrumentation device generating a first sample clock based on the common reference clock;

the first instrumentation device generating a first trigger enable signal based on the first sample clock;

the first instrumentation device receiving a trigger signal from the second instrumentation device; and

the first instrumentation device processing data in response to both receiving the trigger signal and a transition in the first trigger enable signal.

2. The method of claim 1, wherein the first instrumentation device is clocked by the first sample clock for processing data.

3. The method of claim 2, wherein said processing data includes generating or consuming data in response to the sample clock.

4. The method of claim 1, further including:

adjusting a first data path latency of a first output data path included in the first instrumentation device to equal a second data path latency of a second output data path included in the second instrumentation device.

5. The method of claim 1, wherein the transition in the first trigger enable signal is delayed with respect to receiving the trigger signal.

6. The method of claim 1, further including:

configuring the first instrumentation device to generate a first trigger clock, based on the first sample clock.

7. The method of claim 6, further including:

the second instrumentation device generating a second sample clock based on the common reference clock, wherein the second instrumentation device is clocked by the second sample clock for processing data, wherein a phase of the second sample clock is adjusted to a specified phase difference with respect to a phase of the first sample clock; and

configuring the second instrumentation device to generate a second trigger clock, based on the second sample clock, wherein the first trigger clock and the second trigger clock have the same frequency.

8. The method of claim 7, further including:

measuring a phase difference between the first trigger clock and the second trigger clock.

9. The method of claim 8, further including:

adjusting a phase of the first trigger clock in response to measuring a non-zero phase difference.

10. The method of claim 8, further including:

adjusting a phase of the first sample clock, wherein a phase of the first trigger clock is adjusted to a specified phase difference with respect to a phase of the second trigger clock.

11. The method of claim 7, further including:

the second instrumentation device generating a second trigger enable signal based on the second sample clock; and

the second instrumentation device delaying driving the trigger signal until a transition in the second trigger enable signal.

12. The method of claim 11, further including:

the second instrumentation device processing data in response to both receiving the trigger signal and a transition in the second trigger enable signal.

13. The method of claim 11, further including:

the second instrumentation device generating the second trigger enable signal from the second trigger clock, wherein the second trigger enable signal is asserted for one period of the second sample clock each time the second trigger clock transitions from high to low.

14. The method of claim 6, further including:

the first instrumentation device generating the first trigger enable signal from the first trigger clock, wherein the first trigger enable signal is asserted for one first sample clock period each time the first trigger clock transitions from low to high.

15. The method of claim 7, further including:

adjusting a phase of the first trigger clock and a phase of the second trigger clock to a specified phase difference with respect to a phase of the common reference clock.

16. The method of claim 1, further including:

receiving the common reference clock at a third instrumentation device;

the third instrumentation device generating a third trigger enable signal based on a third sample clock, wherein the third instrumentation device generates the sample clock based on the common reference clock, wherein the third sample clock is used by the third instrumentation device for processing data;

the third instrumentation device receiving the trigger signal from the second instrumentation device; and

the third instrumentation device processing data in response to both receiving the trigger signal and a transition in the third trigger enable signal.

17. The method of claim 1, further including:

the first instrumentation device measuring a delay between a transition in the common reference clock and a transition in the first trigger enable signal.

18. The method of claim 17, further including:

adjusting a phase of the first trigger enable signal in response to said measuring.

19. An instrumentation system comprising:

a plurality of instrumentation devices including a first instrumentation device; and

a communication medium configured to couple the plurality of instrumentation devices, wherein a common reference clock is provided to each of the plurality of instrumentation devices, wherein the first instrumentation device generates a first sample clock based on the common reference clock;

wherein the first instrumentation device is configured to generate a first trigger enable signal based on the first sample clock, wherein the first instrumentation device is configured to process data in response to both receiving a trigger signal via the communication medium and a transition in the first trigger enable signal.

20. The instrumentation system of claim 19, wherein the first instrumentation device is clocked by the first sample clock for processing data.

21. The instrumentation system of claim 20, wherein said processing data includes generating or consuming data in response to the sample clock.

22. The instrumentation system of claim 19, wherein the transition in the first trigger enable signal is delayed with respect to receiving the trigger signal.

23. The instrumentation system of claim 19, wherein the first instrumentation device is configured to generate a first trigger clock based on the first sample clock.

24. The instrumentation system of claim 23, wherein the first instrumentation device generates the first trigger enable signal from the first trigger clock, wherein the first trigger enable signal is asserted for one first sample clock period each time the first trigger clock transitions from low to high.

25. The instrumentation system of claim 19, wherein the first instrumentation device measures a delay between a transition in the common reference clock and a transition in the first trigger enable signal.

26. The instrumentation system of claim 19, wherein a phase of the first trigger enable signal is adjusted by the first instrumentation device in response to said measuring.

27. The instrumentation system of claim 22, further including a second instrumentation device, wherein the second instrumentation device generates a second sample clock based on the common reference clock, wherein the second sample clock is used by the second instrumentation device for processing data, wherein a phase of the second sample clock is adjusted to a specified phase difference with respect to a phase of the first sample clock;

wherein the second instrumentation device is configured to generate a second trigger clock, based on the second sample clock, wherein the first trigger clock and the second trigger clock have the same frequency.

28. The instrumentation system of claim 22, wherein a phase difference between the first trigger clock and the second trigger clock is measured by either the first or the second instrumentation device.

29. The instrumentation system of claim 28, wherein in response to measuring a non-zero phase difference, a phase of the first trigger clock is adjusted by either the first or the second instrumentation device.

30. The instrumentation system of claim 28, wherein a phase of the first sample clock is adjusted by either the first or the second instrumentation device, wherein a phase of the first trigger clock is consequently adjusted to a specified phase difference with respect to a phase of the second trigger clock.

31. The instrumentation system of claim 22, wherein the first trigger enable signal is asserted by the first instrumentation device for one period of the sample clock signal in response to an occurrence of a falling edge in the first trigger clock.

32. The instrumentation system of claim 19, wherein each of the plurality of instrumentation devices is configured to generate a respective trigger clock and to drive its respective trigger clock signal onto a front connector.

33. The instrumentation system of claim 22, wherein the first instrumentation device is configured to adjust a phase of the trigger clock to a phase of the common reference clock to a specified phase difference.

34. The instrumentation system of claim 22, wherein the first instrumentation device is coupled to a trigger line, wherein the first instrumentation device is configured to drive the trigger clock onto the trigger line.

35. The instrumentation system of claim 34, further including:

a trigger controller coupled to the trigger line, wherein the trigger controller is configured to measure a phase difference between the first trigger clock and a second trigger clock, wherein the second trigger clock is generated by a second instrumentation device included in the plurality of instrumentation devices.

36. The instrumentation system of claim 35, wherein the trigger controller is coupled to measure a second phase difference between the trigger clock signal and a third trigger clock signal generated by a third instrumentation device included in a different chassis than the plurality of instrumentation devices.

37. The instrumentation system of claim 27, wherein the second instrumentation device is configured to generate a second trigger enable signal, wherein the second instrumentation device is configured to output the trigger signal to the communication medium in response to a transition in the second trigger enable signal.

38. The instrumentation system of claim 19, wherein the first instrumentation device includes an output device, wherein the first instrumentation device is configured to modify a delay of a data path through the output device.