Algorithmically programmable memory tester with history FIFO's that aid in ERROR analysis and recovery

The problem is to branch back to an appropriate location within a memory tester test program, and also restore its state of algorithmic control, when an error associated therewith occurs later in time at the DUT. Owing to delays in pipelines connecting the program execution environment to the DUT and back again. These delays allow the program to arbitrarily advance beyond where the stimulus was given. The arbitrary advance makes it difficult to determine the exact circumstances that were associated with the error. A branch based on the error signal can restart a section of the test program, but it is likely only a template needing further test algorithm control information that varies dynamically as the test program executes. The solution is to equip the memory tester with History FIFO's whose depths are adjusted to account for the sum of the delays of the pipelines, relative to the location of that History FIFO. When the error flag is generated the desired program location and state information is present at the bottom of an appropriate History FIFO. This is also readily applicable when the test program uses an ALU to generate its own DUT stimuli, as well as to the case when the test program/ALU addresses an intermediate Buffer Memory whose contents are central to the nature of the testing the DUT is to undergo. The first is an ALU History FIFO, while the second is a Buffer Memory History FIFO. There can also be ECR History FIFO's. There is a mechanism to track system re-configuration as it occurs and adjust the depths of the various History FIFO's according to resulting pipeline depth. There is a mechanism to freeze the contents of a History FIFO upon the generation of an error. A History FIFO can be extended to allow a branching instruction in the test program to not prematurely respond to an error flag sooner than the pipeline delay needed for that error flag's value to be determined by a cause located within the test program.