Integrated circuit signature analyzer for testing digital circuitry

• US 4,897,842 A
• Filed: 11/05/1987
• Issued: 01/30/1990
• Est. Priority Date: 11/05/1987
• Status: Expired due to Fees

• Current Assignee: Ampex Corporation (Delta Information Systems, Inc.)
• Original Assignee: Ampex Corporation (Delta Information Systems, Inc.)
• Inventors: Herz, William S., Williams, Robert A.
• Primary Examiner(s): ATKINSON, CHARLES
• Application Number:
  US07/117,772
• Time in Patent Office: 817 Days
• Field of Search: 371/25, 371/61, 324/73 R, 324/73 AT, 324/73 PC
• US Class Current: 714/732
• CPC Class Codes: G06F 11/277 with comparison between actual response and known fault-free response

Abstract

A system for testing digital circuitry includes a signature generator that is connected to a plurality of nodes in the circuit to be tested and that generates signature words unique to identical streams of binary data signals or clocking signals. A multiplexer sequentially directs streams of signals to the signature generator from selected test nodes, or data streams from a plurailty of nodes can be signaturized simultaneously.

Claims

1. A system for testing digital electronic circuits comprising:

generator means integrated with circuits to be tested for generating words that are unique to identical streams of binary signals;

connecting means that connect the generator means to receive binary signals from a plurality of nodes in the digital circuit to be tested such that the generator means is simultaneously provided with bit streams from more that two nodes of the plurality of nodes; and

comparator and storage means for receiving, storing and comparing consecutively-generated signature words.

2. A system for testing the stability of streams of binary signals at multiple nodes in electronic digital circuits comprising:

generator means connected for receiving binary bit streams simultaneously from at least two nodes and operative for producing signature words unique to identical streams of binary signals;

selector means that connect the generator means to receive streams of binary signals from at least two nodes in the digital circuit to be tested;

comparator means that receive and compare consecutive signature words generated by the generator means; and

means responsive to the comparator means for indicating the presence and absence of identity between consecutively-generated signature words.

3. A system according to claim 2 further including counter means responsible to the comparator means to count the number of consecutive identical signature words generated by the generator means.

4. A system according to claim 2 wherein the connecting means comprises a multiplexer means that receives the bit streams from the nodes and directs the streams sequentially to the generator means.

5. A system for detecting the stability of clock intervals in streams of clocking signals in digital electronic circuits comprising:

generator means connected to the nodes of a circuit under test to generate signature words unique to identical streams of edges of clock signals;

comparator means connected to the generator means for comparing consecutive signature words generated by the generator means; and

means connected to the comparator means for indicating lack of identity between consecutively-generated signature words and, thereby for indicating whether clocking intervals are stable.

6. A system according to claim 5 further including memory means that stores signature words for comparison with the signature words generated by the signature generator means.

7. A process for testing digital electronic circuitry with an integral signature analyzer comprising the steps of:

from a plurality of nodes of the circuit to be tested, directing simultaneous streams of binary data to a signature generator;

generating signature words that are unique to identical streams of binary data;

comparing generated signature words with signature words that are stored in a memory device;

comparing consecutively-generated signature words; and

indicating the presence and absence of identity between compared signature words.

8. A process according to claim 7 including the step of counting the number of consecutive signature words that are identical.

9. A process according to claim 17 wherein, after an indication is obtained that two consecutive signature words are different, streams of binary data are directed to the signature analyzer serially and sequentially from nodes to be tested.

10. A process according to claim 22 including the steps of obtaining signature words from nodes of a correctly operating circuit of the same kind as the one under test, and storing the obtained signature words in an external memory device.

11. A process for testing the stability of clocking intervals in digital electronic circuits comprising the steps of:

directing streams of clocking pulses to a signature analyzer;

generating signature words that are unique to identical streams of clocking pulses;

comparing consecutively-generated signature words; and

indicating the presence and absence of identity between consecutive signature words.

12. A process according to claim 11 further including the steps of comparing generated signature words with signature words that are generated from correctly operating circuits of the same kind as the one under test.

13. A system for testing digital electronic circuits comprising:

generator means integrated with circuits to be tested and selectively connectable for generating signature words in response to edges of clocking signals, which words are unique to identical streams of binary signals;

connecting means that connect the generator means to receive binary signals from a plurality of nodes in the digital circuit to be tested; and

comparator means connected to receive and compare signature words generated by the generator means with stored signature words to indicate the stability of clocking intervals for the circuits being tested.