Memory tester with enhanced post decode

Abstract

The data path into a post decode mechanism is altered to allow post decode to process data before or as that data is placed into a destination memory structure in interior test memory. Other data will continue to be first placed into a memory structure in interior test memory before being applied to the post decode mechanism. Extensive masking capability coupled with copies of error tables allow incremental post decode analysis for a new test, and avoids counting of errors in locations that are already known to have failed during previous tests. Both errors within words and bit errors can be accumulated. The post decode mechanism is often capable of producing multiple type of results from a single pass through the data, whether applied on the fly or from a structure in interior test memory. The post decode mechanism has counters that count down from pre-loaded values representing thresholds for deciding something about error activity. A counts of zero produces a terminal count flag. The values of the various terminal count flags are available at any time as data to be logged in interior test memory. Counters are often reloaded with an initial count at the conclusion of one test phase and in preparation for a subsequent phase. Some overhead may be saved and utility added by arranging for the counters to have respective initial value registers from which they may be reloaded upon receipt of a single command. The presence of the terminal count flag for a counter can inhibit the reload of the counter from its initial value register.