ABSTRACT
This chapter presents a new design of Test Access Port (TAP) that provides a means to arbitrarily observe test results and source test stimulus. TAP is to be built in printed circuit board (PCB) and shared between several Integrated Circuits (ICs). Exploiting TAP in controlling the testing system increases the diagnostic efficiency, reliability and flexibility. TAP resources waive the tester design from the need of the most costly parts such as memory and microcontroller. PCB testing is becoming more expensive and difficult due to the complexity of PCBs design. The common methods for diagnosing PCBs are still suffering from many difficulties; it needs a long time, a lot of manual work, and direct contact with PCB, and it is so expensive. PCB includes many ICs on a single board, each of which is separately designed and verified before use. During handling or even manufacturing PCBs and ICs, defects may develop.
