TEST STANDARD SPEEDS ON-BOARD PROGRAMMING

The IEEE 1149.1 standard (commonly referred to as JTAG, after the Joint Test Action Group, which initiated the process) was developed to test PC-board trace continuity without using physical probes. A set of serially connected cells capture and drive data, which can be shifted out serially and compared with experimental results. The JTAG circuitry includes various registers and a finite, synchronous state machine controlled by dedicated pins.