Patent ID: 6834364
Filing Date: 2004-12-21
Classification: G11C

Abstract:
A method of producing a representation of voltage waveforms for selected channels of a Device Under Test (DUT) operated by a tester that executes a test program having an algorithmic nature that includes branching based on responses of the DUT to stimuli provided by the test program, the method comprising the steps of:(a) generating a trigger signal indicative of the simultaneous occurrence of selected conditions within the hardware of the tester, including the execution of a selected portion of the test program; (b) subsequent to an initial generation of the trigger signal by step (a), capturing a target sequence of addresses that correspond to a target sequence of instructions that is a selected number of consecutive instructions executed by the test program following the occurrence of the trigger signal; (c) subsequent to step (b), fetching the target sequence of instructions identified by the captured target sequence of addresses; (d) subsequent to step (c), altering the fetched target sequence of instructions to adjust any branching therein to point to the next instruction in the sequence thereof; (e) subsequent to step (d), storing the altered target sequence of instructions in a reserved portion of a program memory from which the test program is executed; and then (f) repeatedly, and in the order specified below, until step (f6) has stored a sufficient amount of comparison results to allow the production of the representation of the voltage waveforms for the selected channels: (f1) re-starting the test program; (f2) generating a subsequent instance of the trigger signal; (f3) interrupting the execution of the test program; (f4) putting into effect for the selected channels selected values of a voltage comparison threshold and a sample timing offset; (f5) resuming the execution of the test program at the start of the stored altered target sequence of instructions; (f6) storing comparison results for the selected channels; and then: (g) producing from the stored comparison results a representation of the voltage waveforms for the selected channels.