Test Access Port & Scan Based Technique of In-System Timing Extraction and Control

Historically, most Printed Circuit Board (PCB) testing was done using bed-of-nail in-circuit test equipment. The progress in the field of miniaturization and integration density has possible to design very complex PCBs, which presents very high testability requirements. Boundary scan is now the most promising technology for testing high complexity PCBs. This paper presents scan-based test access port standard for testing complex ICs and also presents a method which allow the extraction of fine-grained timing information using Test Access Port (TAP).