Automatic test equipment

• US 4,807,161 A
• Filed: 12/29/1987
• Issued: 02/21/1989
• Est. Priority Date: 11/25/1983
• Status: Expired due to Fees

• Current Assignee: Mars Incorporated
• Original Assignee: Mars Incorporated
• Inventors: Comfort, John J., Mason, Brian R., Kargathra, Dinesh, Hayter, Paul A., Fisher, Ian R., Turner, Graham N., Bailey, John W.
• Primary Examiner(s): Harkcom, Gary V.
• Assistant Examiner(s): HERNDON, HEATHER R
• Application Number:
  US07/140,895
• Time in Patent Office: 420 Days
• Field of Search: 364/550, 364/551, 364/709, 364/579, 364/571, 324/73 PC, 324/73 AT
• US Class Current: 702/121
• CPC Class Codes: G01R 31/2637 for testing other individual devices G01R31/2608 - G01R31/2632, G01R31/27 take precedence
• CPC Class Codes: G01R 31/31907 Modular tester, e.g. controlling and coordinating instruments in a bus based architecture
• CPC Class Codes: G01R 31/31912 Tester/user interface
• CPC Class Codes: G01R 31/31926 Routing signals to or from the device under test [DUT], e.g. switch matrix, pin multiplexing
• CPC Class Codes: G06F 11/261 by simulating additional hardware, e.g. fault simulation
• CPC Class Codes: G06F 11/277 with comparison between actual response and known fault-free response

Abstract

An automatic test equipment for the functional testing of electrical printed circuit board assemblies is constructed as the combination of a programmable controller based upon a microcomputer and selected interface modules which can be plugged into the controller system backplane in any of a number of module interconnection locations and in any combination of module types with the controller being adapted to interrogate the modules as to their type and location and organize its routines accordingly. The controller has an advantageous bus structure for resource sharing within the equipment, and provides facilities for various forms of input/output modules as well as for analog stimulus/response modules, programmable waveform generator modules, signature analysis and frequency measurement modules, real time emulation modules, etc., and for the connection of computer standard utilities such as keyboard, light-pen graphics, printer, etc., as well as specialist instrumentation and also a manufacturing defects analyzer for in-circuit testing.

Claims

1. Automatic test equipment for the functional testing of electronic circuits, said automatic test equipment comprising:

a programmable controller comprising a digital computer having keyboard and display facilities;

first means for the connection to said programmable controller of a number of testing devices such as power supplies and external specialist instrumentation;

second means for the connection to said programmable controller of a user configured number of optional testing devices, said second means comprising a plurality of function module connection sites provided in the automatic test equipment with each of said connection sites being capable of receiving any one of a plurality of different function modules of predetermined type designed to be controlled by the controller;

a user-configured selection of optional function modules comprising a plurality of such modules received in selected ones of said connection sites, each of said optional function modules being adapted to be controlled by the controller in the performance of predetermined specific circuit testing operations and including means to enable the function module type, as regards its functional capability, to be determined by the controller;

connector means for coupling said plurality of function modules to an electronic circuit to be tested; and

a bus structure interconnecting said plurality of function module connection sites with each other and with said programmable controller in a shared resource arrangement providing for direct module-to-module communication, said bus structure comprising;

(i) a computer databus for communicating control data from the controller to the function modules for controlling the operation of the function modules and for passing digital data to and from the function modules;

(ii) a function module indentification bus for enabling the controller to identify individual function module types and ascertain their locations in said plurality of module connection sites;

(iii) analog stimulus and analog measurement buses enabling the sharing of analog resources within the automatic test equipment by direct communication between function modules received in said connection sites of analog stimulus and response signals; and

(iv) a synchronization bus comprising a plurality of sync/digital common lines for enabling direct module-to-module communication for cross-synchronization of events occurring within the automatic test equipment.

2. Automatic test equipment as claimed in claim 1 wherein said optional function modules include at least one frequency measurement module.

3. Automatic test equipment as claimed in claim 2 wherein the frequency measurement module includes a frequency shift detector comprising a counter arranged to assemble a count of the number of cycles of an incoming frequency signal occurring within a set measurement period, first and second latches serially connected to the counter output, means for transferring the count accumulated in said counter to said first latch and for transferring the contents of said first latch into said second latch once every N measurement periods, N being an integer of at least one, and a comparator for comparing the contents of the latches one with the other and providing an output indicative of detected differences.

4. Automatic test equipment as claimed in claim 1 wherein the keyboard includes a plurality of special function keys the operations of which are changeable under software control and the display facility is arranged to provide to a user an indication as to the current functions of said special function keys.

5. Automatic test equipment as claimed in claim 4 wherein said special function keys are each distinctively coloured and the display facility is arranged to include a correspondingly coloured indicia in the indication provided to a user of the current function of each special function key.

6. Automatic test equipment as claimed in claim 1 wherein said display facility includes a light pen and the microcomputer is arranged to enable a user to draw in signal sequences and waveform shapes to be used in the testing of an electronic circuit.

7. Automatic test equipment as claimed in claim 1 wherein, in order to enable the controller to determine the type of function module associated with any of said module connection sites, type identifying code means are associated with each of said modules, and said controller is arranged for interrogating said module connection sites to ascertain the nature of the code means associated with modules received therein whereby to assemble in said controller a map indicating what module type is received in which connection site.

8. Automatic test equipment as claimed in claim 1 wherein said optional function modules include at least one multi-bit digital input/output module wherein a plurality of signal lines are individually configurable selectively as one of an input and an output and are dynamically changeable through operation of the programmable controller.

9. Automatic test equipment as claimed in claim 8 wherein said multi-bit digital input/output module is user configurable through operation of the programmable controller for determined threshold levels for logic one and logic zero inputs and outputs.

10. Automatic test equipment as claimed in claim 1 wherein said optional function modules include at least one isolated logic digital input/output module providing a plurality of opto-isolated logic inputs and a plurality of single-pole single-throw isolated relay switch outputs.

11. Automatic test equipment as claimed in claim 1 wherein said optional function modules include at least one digitally controllable programmable waveform generator module for generating user definable analog waveform shapes for use as circuit testing inputs.

12. Automatic test equipment as claimed in claim 11 wherein said digitally controllable programmable waveform generator module comprises a random access memory device the data contents whereof can be loaded by a user through operation of the controller, a variable rate clock generator controllable in dependence upon a user determinable digital signal, a counter driven by the output of said variable rate clock generator and providing a control input to said random access memory device, a latch circuit coupled to the output of said random access memory device, and a multiplying digital-to-analog converter coupled to the output of said latch circuit and having a multiplying factor which is controllable in dependence upon a user determinable digital signal.

13. Automatic test equipment as claimed in claim 12 wherein a user-selectable read only memory device is provided in parallel with said random access memory device and is preprogrammed with a plurality of predetermined standard waveform shapes.

14. Automatic test equipment as claimed in claim 12 wherein first and second counters are provided and each is capable of independently controlling the operation of a said random access memory device, the arrangement being such as to enable the generation of first and second signals having a phase interrelationship determined according to the user controllable setting of said first and second counters.

15. Automatic test equipment as claimed in claim 1 wherein said optional functional modules include at least one analog stimulus/response module.

16. Automatic test equipment as claimed in claim 15 wherein said analog stimulus/response module is arranged to be digitally controllable by a user through operation of said controller and comprises a plurality of digital-to-analog and analog-to-digital converter channels.

17. Automatic test equipment as claimed in claim 1 wherein said optional function module include at least one module adapted for waveform analysis and signal sequence recognition.

18. Automatic test equipment as claimed in claim 17 wherein said waveform analysis and signal sequence recognition module is adapted to perform at least one of a signature analysis technique, a transition counting technique, and a logically combined signature analysis and transition counting technique.

19. Automatic test equipment as claimed in claim 18 wherein an incoming data stream to be recognized by said module is supplied to a feedback shift register adapted to generate a pseudo-random sequence that is a function of the input data stream at specific clocked time intervals, and is also supplied to a digital counter arranged to be clocked in response to transitions of the incoming data stream, and the outputs of said feedback shift register and said digital counter are combined to constitute a recognizable signature.

20. Automatic test equipment as claimed in claim 19 wherein the outputs of said feedback shift register and of said digital counter are combined by one of a process of concatenation, a process of bit-by-bit exclusive OR gating, and a process of bit-by-bit addition.

21. Automatic test equipment as claimed in claim 19 wherein said feedback shift register is arranged to provide a maximal length sequence for steady one or zero data inputs.

22. Automatic test equipment as claimed in claim 17 wherein said waveform analysis and signal sequence recognition module comprises a plurality of data inputs;

a CLOCK input multiplexer, a SET input multiplexer, and a RESET input multiplexer coupled to said data inputs;

a single period detector having a SET input coupled to the output of the SET input multiplexer and a RESET input coupled to the output of the RESET input multiplexer;

a programmable counter having a CLOCK input coupled to the output of the CLOCK multiplexer and having an ENABLE input coupled to the output of the single period detector; and

a feedback shift register coupled to the output of the programmable counter and having an ENABLE input coupled to the ENABLE input of the programmable counter, a CLOCK input, and a TEST DATA input.

23. Automatic test equipment as claimed in claim 22 wherein edge polarity determining gating means are coupled between the outputs of the SET and RESET multiplexers and the SET and RESET inputs of the single period detector.

24. Automatic test equipment as claimed in claim 22 wherein a binary counter providing a missing pulse detection output is coupled to receive the ENABLE input from the single period detector, the CLOCK input to the feedback shift register, and a CLEAR input coupled to the TEST DATA input of the feedback shift register.

25. Automatic test equipment as claimed in claim 1 wherein said optional function modules include at least one switching module enabling selected circuit nodes of a unit under test to be accessed selectively for measurement and stimulus purposes.

26. Automatic test equipment as claimed in claim 1 wherein said optional function modules include at least one active jig interface module for connection to a unit under test by means of a bed-of-nails type of testing jig, said active jig interface module comprising a plurality of controllable switches for coupling circuit nodes of a unit under test to respective ones of measurement, stimulus and reference lines.

27. Automatic test equipment as claimed in claim 1 wherein said optional function modules include at least one real time sequence emulator module providing a plurality of bits of digital input/output individually configurable as inputs or outputs capable of bursts of real time activity.

28. Automatic test equipment as claimed in claim 27 wherein said real time sequence emulator module comprises a digital sequence controller, a sequence random access memory device and an associated latch in a circulatory data path with said sequence controller, a control random access memory device, a data random access memory device, means for loading and retrieving data into and from said random access memory devices, a second latch associated with said control random access memory device, a third latch associated with said data random access memory device, a first gating device operable to condition an output of said first latch as an output to a data line, a second gating device operable to enable data from said data line to be written into said data random access memory device and into said third latch, and direction control logic for determining the condition of said gating devices in dependence upon an output from said second latch, said sequence controller being arranged to provide random access memory device addresses to said control and data random access memory devices for determining the operation thereof.

29. Automatic test equipment as claimed in claim 28 wherein means are provided for comparing data outputted by said third latch with data incoming from said data line, the arrangement being such that data corresponding to that expected from an input may be loaded into the data random access memory device and therefrom into the third latch for comparison with actual incoming data, the output of said comparing means thereby being indicative of the relationship between the actual and expected data.

30. Automatic test equipment as claimed in claim 19 wherein the output of said comparing means is coupled as an input to said data random access memory device for assembling therein a signature matrix indicating success or failure of circuit tests.

31. Automatic test equipment as claimed in claim 27 wherein said emulator module comprises a master emulator and a plurality of slave emulators controlled by the master emulator, the master emulator comprising control circuitry for up to a predetermined number of slave emulators and the slave emulators each comprising a plurality of RAM backed digital input/output lines each dynamically changeable between input and output states.

32. Automatic test equipment as claimed in claim 31 wherein each digital input/output line of a slave emulator is backed by a stimulus RAM for providing test stimulus data patterns, a response RAM for collecting responses from a unit under test, and a direction control RAM for determining the reading and writing states of the respective line.

33. Automatic test equipment as claimed in claim 32 wherein the slave emulator modules further comprise comparators for effecting at least one of detecting differences between data received from a unit under test and data received from a respective stimulus RAM, and comparing data patterns on the slave emulator input, output lines with at least one predetermined data pattern.

34. Automatic test equipment as claimed in claim 27 wherein said sequence emulator module comprises a random access memory structure for storage of microprocessor emulation data and micro-instruction codes are stored in said random access memory structure, said codes defining the data transfer instructions of the microprocessor to be emulated.

35. Automatic test equipment as claimed in claim 34 wherein said random access memory structure comprises stimulus, response and direction control RAM'"'"'s and said micro-instruction codes comprise sequences of patterns stored in said RAMs for defining the stat of individual signal lines in the sequence required for the respective emulation.

36. Automatic test equipment as claimed in claim 1 wherein at least one of said optional function modules comprises a manufacturing defects analyzer module for testing the viability of components on a printed circuit board, said module including an array of bidirectionally current conducting switching networks each defining a test point for connection to a node of printed circuit board under test and connectable by control of the respective switching network selectively to one of a stimulus source and a reference potential and simultaneously also to a corresponding input of a measurement facility.

37. Automatic test equipment as claimed in claim 36 wherein said switching networks each comprise four bidirectionally current conducting analog switches each comprising a control electrode to which an input may be applied for determining the current conduction condition of the respective switch, a first of said switches having its current conduction path connected between a stimulus source terminal and the respective test point and its control electrode connected to a first selection terminal, a second of said switches having its current conduction path connected between said test point and a reference potential terminal and its control electrode connected to a second selection terminal, a third of said switches having its current conduction path connected between said test point and a first measurement terminal and its control electrode connected to a third selection terminal, and a fourth of said switches having its current conduction path connected between said test point and a second measurement terminal and its control electrode connected to a fourth selection terminal.

38. Automatic test equipment as claimed in claim 37 wherein said first and said third selection terminal are commonly connected, and said second and said fourth selection terminal are commonly connected.

39. Automatic test equipment as claimed in claim 38 wherein said switches each comprise a bidirectional analog transmission gate.

40. Automatic test equipment as claimed in claim 1 in combination with one or more signal measurement and/or injector probes including an integral display for indicating to a user of the equipment information such as, for example, a designation of the next point to be probed in a sequence controlled by the system software.

41. Automatic test equipment as claimed in claim 1 adapted and arranged such that, in operation of the equipment, the equipment provides a user of the equipment with a sequence of instructions derived on a question and answer basis and designed to lead the user through the operations required for creating a required interface with a unit under test and defining the required test program.

42. Automatic test equipment as claimed in claim 1 including means responsive to the manual representation by a user of the equipment of a test signal to be utilized in the operation of the equipment for deriving a corresponding test signal.

43. Automatic test equipment as claimed in claim 42 wherein said means for deriving a test signal corresponding to a manual representation of a user comprises a light pen and a graphics facility utilizable with said light pen.

44. Automatic test equipment for the functional testing or electronic circuits, said automatic test equipment comprising:

a programmable controller comprising a digital computer having keyboard and display facilities;

first means for the connection to said programmable controller of a number of testing devices such as power supplies and external specialist instrumentation;

second means for the connection to said programmable controller of a user configured number of optional testing devices, said second means comprising a plurality of function module connection sites provided in the automatic test equipment with each of said connection sites being capable of receiving any one of a plurality of different function modules of predetermined type designed to be controlled by the controller;

a user-configured selection of optional function modules comprising a plurality of such modules received in selected ones of said connection sites, each of said optional function modules being adapted to be controlled by the controller in the performance of predetermined specific circuit testing operations and including means to enable the function module type, as regards its functional capability, to be determined by the controller;

connector means for coupling said plurality of function modules to an electronic circuit to be tested; and

a bus structure interconnecting said plurality of function module connection sites with each other and with said programmable controller in a shared resource arrangement providing for direct module-to-module communication, said bus structure comprising;

(i) computer databus for communication control data from the controller to the function modules for controlling the operation of the function modules and for passing digital data to and from the function modules; and

(ii) a function module identification bus for enabling the controller to identify individual function module types and ascertain their locations in said plurality of module connection sites.

45. Automatic test equipment as claimed in claim 44, said bus structure further comprising a synchronization bus comprising a plurality of sync/digital common lines for enabling direct module-to-module communication for cross-synchronization of events occurring within the automatic test equipment.

46. Automatic test equipment as claimed in claim 44, said bus structure further comprising analog stimulus and analog measurement buses enabling the sharing of analog resources within the automatic test equipment by direct communication between function modules received in said connection sites of analog stimulus and response signals.

47. Automatic test equipment for the functional testing of electronic circuits, said automatic test equipment comprising:

a programmable controller comprising a digital computer having keyboard and display facilities;

first means for the connection to said programmable controller of a number of testing devices such as power supplies and external specialist instrumentation;

second means for the connection to said programmable controller of a user configured number of optical testing devices, said second means comprising a plurality of function module connection sites provided in the automatic test equipment with each of said connection sites being capable of receiving any one of a plurality of different function modules of predetermined type designed to be controlled by the controller;

a user-configured selection of optional function modules comprising a plurality of such modules received in selection ones of said connection sites, each of said optional function modules being adapted to be controlled by the controller in the performance of predetermined specific circuit testing operations and including means to enable the function module type, as regards its functional capability, to be determined by the controller;

connector means for coupling said plurality of function modules to an electronic circuit to be tested; and

a bus structure interconnecting said plurality of function module connection sites with each other and with said programmable controller in a shared resource arrangement providing for direct module-to-module communication, said bus structure comprising;

(i) a computer data bus for communicating control data from the controller to the function modules for controlling the operation of the function modules and for passing digital data to and from the function modules; and

(ii) analog stimulus nd analog measurement buses enabling the sharing of analog resources within the automatic test equipment by direct communication between function modules received in said connection sites of analog stimulus and response signals.

48. Automatic test equipment as claimed in claim 47, said bus structure further comprising a synchronization bus comprising a plurality of sync/digital common lines for enabling direct module-to-module communications for cross-synchronization of events occurring within the automatic test equipment.

49. Automatic test equipment for the functional testing of electronic circuits, said automatic test equipment comprising:

a programmable controller comprising a digital computer having keyboard and display facilities;

first means for the connection to said programmable controller of a number of testing devices such as power supplies and external specialist instrumentation;

second means for the connection to said programmable controller of a user configured number of optional testing devices, said second means comprising a plurality of function module connection sites provided in the automatic test equipment with each of said connection sites being capable of receiving any one of plurality of different function modules of predetermined type designed to be controlled by the controller;

a user-configured selection of optional function modules comprising a plurality of such modules received in selected ones of said connection sites, each of said optional function modules being adapted to be controlled by the controller in the performance of predetermined specific circuit testing operations and including means to enable the function module type, as regards its functional capability, to be determined by the controller;

connector means for coupling said plurality of function modules to an electronic circuit to be tested; and

a bus structure interconnecting said plurality of function module connection sites with each other and with said programmable controller in a shared resource arrangement providing for direct module-to-module communication, said bus structure comprising;

(i) a computer databus for communicating control data from the controller to the function modules for controlling the operation of the function modules and for passing digital data to and from the function modules; and

(ii) a synchronization bus comprising a plurality of sync/digital common lines for enabling direct module-to-module communication for cross-synchronization of events occurring within the automatic test equipment.