Presented is test system for use in debugging functional and electrical failures of an integrated circuit. The test system includes a diagnostics retrieval system and a test access port retrieval system external to the integrated circuit under test, and a debug trigger apparatus and test access...http://www.google.de/patents/US5771240?utm_source=gb-gplus-sharePatent US5771240 - Test systems for obtaining a sample-on-the-fly event trace for an integrated circuit with an integrated debug trigger apparatus and an external pulse pin 
