IEEE Standards related to DFT

Analog or Mixed signal circuitry is left out by IEEE 1149.1. Recognizing this shortcoming, an IEEE working group was formed in the early 1990s with the purpose to develop a standardized test access methodology for analog and mixed signal pins. In 1999 the effort resulted in the approval of the IEEE Std. 1149.4 (Standard for a Mixed Signal Test Bus). The purpose of this standard is to provide the means to measure and characterize device level or board level mixed-signal and analogue parameters. IEEE 1149.4 compliant devices (which are also 1149.1 compliant) feature two additional test bus signals (AT1 and AT2). These two test bus signals can be connected to I/O pins through a switching structure (TBIC and ABM) for the purpose of test. Typically, they are used to provide a constant current to one pin and to measure the voltage on that and another pin (one by one). This test approach is used to measure resistance and capacities in the circuitry.

DFT Guide

IEEE 1149.4 Summary

Main Menu

GOEPEL Electronics