Algorithmically programmable memory tester with breakpoint trigger, error jamming and 'scope mode that memorizes target sequences

Abstract

A trigger signal for a memory tester uses a (breakpoint) trigger qualified according to what part of the test program is being executed. The qualified breakpoint trigger can be delayed before becoming a system trigger signal that can be used to trigger a 'scope mode and to force an error flag to a selected value so as to compel a particular path with the test program. To provide stable waveforms for the sweeping of the voltage thresholds and sample timing offset the memory tester records the addresses for a target sequence of transmit vectors issued during an initial pass through the test program subsequent to the occurrence of the trigger. These addresses are exchanged for the instructions themselves, which are then altered to remove branching, and stored in a reserved portion of the memory they came from. Once the altered target sequence is stored the desired information is produced by restarting the entire test program and letting it run exactly as before down to the trigger. Now when the trigger occurs further transmit vectors are issued from the memorized target sequence, rather than from the live algorithm, and a combination of voltage thresholds and the sample timing offset are switched into place. After the target sequence the test program is re-started with normal thresholds and sample timing offsets. There is eventually another trigger, whereupon the memorized target sequence is again substituted while the next combination in the step along the acquisition sweep is instituted. This process is continued until the entire acquisition sweep has been performed. An inspection of the stored data allows creation of the waveforms.