System and method for synchronizing multiple instrumentation devices

• US 20040064750A1
• Filed: 09/30/2002
• Published: 04/01/2004
• 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 M.
• Granted Patent: US 7,240,231 B2
• Time in Patent Office: Days
• US Class Current: 713/401
• 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. 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 the first instrumentation device is configured to process data in response to a sample clock signal and to generate a first trigger enable signal, wherein the first instrumentation device is configured to delay performing an operation in response to a trigger signal transmitted to the first instrumentation device via the communication medium until a transition in the first trigger enable signal;

wherein the first trigger enable signal is not the sample clock signal.

2. The instrumentation system of claim 1, wherein a second instrumentation device included in the plurality of instrumentation devices is configured to generate a second trigger enable signal, wherein the second instrumentation device is configured to delay performing an operation in response to the trigger signal transmitted via the communication medium until a transition in the second trigger enable signal.

3. The instrumentation system of claim 2, wherein the first trigger enable signal is synchronized to the second trigger enable signal.

4. The instrumentation system of claim 1, wherein the first instrumentation device includes a first trigger enable signal generator coupled to receive the sample clock signal, wherein the first trigger enable signal generator is configured to generate a trigger clock signal that has a frequency equal to 1/N of a frequency of the sample clock signal, where N is greater than or equal to 1.

5. The instrumentation system of claim 4, wherein the trigger clock signal is the first trigger enable signal.

6. The instrumentation system of claim 4, wherein the first trigger enable signal generator includes a counter configured to increment a count in response to each rising edge of the sample clock signal, wherein the counter is configured to generate the trigger clock signal.

7. The instrumentation system of claim 4, wherein the first trigger enable signal generator is configured to assert the first trigger enable signal for one period of the sample clock signal in response to an occurrence of a falling edge in the trigger clock signal.

8. The instrumentation system of claim 7, wherein the first trigger enable signal generator is configured to assert a second trigger enable signal for one period of the sample clock signal in response to an occurrence of a rising edge in the trigger clock signal.

9. The instrumentation system of claim 8, wherein the first instrumentation device is configured to drive a second trigger signal on the communication medium in response to a rising edge of the second trigger enable signal.

10. The instrumentation system of claim 4, wherein each of the plurality of instrumentation devices is configured to generate a respective trigger clock signal and to drive its respective trigger clock signal onto a front connector.

11. The instrumentation system of claim 4, wherein the first instrumentation device is configured to lock a phase of the trigger clock signal to a phase of a reference clock signal conveyed to the first instrumentation device via the communication medium.

12. The instrumentation system of claim 4, wherein the first instrumentation device is coupled to a trigger line, wherein the first instrumentation device is configured to drive the trigger clock signal onto the trigger line.

13. The instrumentation system of claim 12, further comprising a trigger controller coupled to the trigger line, wherein the trigger controller is configured to measure a phase difference between the trigger clock signal and a second trigger clock signal generated by a second instrumentation device included in the plurality of instrumentation devices.

14. The instrumentation system of claim 13, 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.

15. The instrumentation system of claim 1, wherein the first instrumentation device includes a delay unit configured to measure a delay between a transition in a reference signal and a transition in the first trigger enable signal.

16. The instrumentation system of claim 15, wherein the first instrumentation device is configured to output data indicative of the delay.

17. The instrumentation system of claim 16, wherein the first instrumentation device is configured to receive data indicative of an amount of compensation, wherein the first instrumentation device is configured to adjust a phase of the first trigger enable signal in response to the data indicative of the amount of compensation.

18. The instrumentation system of claim 17, wherein the first instrumentation device adjusts the phase of the first trigger enable signal by adjusting a current value of a counter.

19. The instrumentation system of claim 18, further including a host computer system configured to receive the data indicative of the delay, to responsively generate the data indicative of an amount of compensation, and to output the data indicative of the amount of compensation.

20. The instrumentation system of claim 1, wherein a second instrumentation device included in the plurality of instrumentation devices 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.

21. The instrumentation system of claim 1, 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 in response to receiving data indicative of a new delay of the data path through the output device.

22. The instrumentation system of claim 1, wherein the plurality of instrumentation devices are configured to provide digital stimulus in concert with each other.

23. The instrumentation system of claim 1, wherein the plurality of instrumentation devices is configured as a stimulus/response system.

24. A method comprising:

a first instrumentation device processing data in response to a sample clock signal;

the first instrumentation device generating a trigger enable signal;

a second instrumentation device communicating a trigger signal to the first instrumentation device; and

the first instrumentation device delaying performance of an operation in response to the trigger signal until a transition in the trigger enable signal.

25. The method of claim 24, further comprising the first instrumentation device generating the sample clock signal.

26. The method of claim 25, further comprising:

the second instrumentation device generating a second sample clock signal; and

aligning a phase of the sample clock signal to a phase of the second sample clock signal.

27. The method of claim 25, further comprising configuring the first instrumentation device to generate a first trigger clock signal having the same frequency as a second trigger clock signal generated by the second instrumentation device.

28. The method of claim 27, wherein said configuring comprises programming a first counter included in the first instrumentation device with a rollover value, wherein a second counter included in the second instrumentation device is programmed with the rollover value.

29. The method of claim 27, further comprising measuring a phase difference between the first trigger clock signal generated by the first instrumentation device and the second trigger clock signal generated by the second instrumentation device.

30. The method of claim 29, further comprising adjusting a phase of the first trigger clock signal generated by the first instrumentation device in response to measuring a nonzero phase difference.

31. The method of claim 27, further comprising the second instrumentation device delaying driving the trigger signal onto a communication medium until a transition in a second trigger enable signal generated by the second instrumentation device.

32. The method of claim 31, further comprising the second instrumentation device generating the second trigger enable signal from the second trigger clock signal, wherein the second trigger enable signal is asserted for one period of the second sample clock signal each time the second trigger clock signal transitions from high to low.

33. The method of claim 27, further comprising the first instrumentation device generating the trigger enable signal from the first trigger clock signal, wherein the trigger enable signal is asserted for one sample clock period each time the first trigger clock signal transitions from low to high.

34. The method of claim 33, further comprising the first instrumentation device generating a second trigger enable signal and delaying communicating a second trigger signal to the second instrumentation device until a transition in the second trigger enable signal, wherein the second trigger enable signal is asserted for one sample clock period each time the first trigger clock signal transitions from high to low.

35. The method of claim 27, further comprising measuring a phase difference between the first trigger clock signal and the second trigger clock signal.

36. The method of claim 35, further comprising adjusting a phase of the first trigger clock signal in response to said measuring.

37. The method of claim 27, further comprising locking a phase of the first trigger clock signal and a phase of the second trigger clock signal to a phase of a reference clock signal.

38. The method of claim 24, further comprising 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.

39. The method of claim 24, wherein said processing comprises generating or consuming data in response to the sample clock signal.

40. The method of claim 24, further comprising a third instrumentation device generating a third trigger enable signal and delaying performance of an operation in response to the trigger signal until a transition in the third trigger enable signal.

41. The method of claim 24, further comprising the first instrumentation device measuring a delay between a transition in a reference signal and a transition in the trigger enable signal.

42. The method of claim 24, further comprising compensating a phase of the trigger enable signal in response to said measuring.

43. A system comprising:

a plurality of devices including a first device; and

a communication medium configured to couple the plurality of devices;

wherein the first device is configured to process data in response to a sample clock signal and to generate a first trigger enable signal, wherein the first device is configured to delay performing an operation in response to a trigger signal transmitted to the first device via the communication medium until a transition in the first trigger enable signal;

wherein the first trigger enable signal is not the sample clock signal.