Why 1149.1 (JTAG) really works

The IEEE 1149.1 boundary-scan standard (JTAG) has now been a reality for over four years, and has had a lot of success, not always in the ways that the pioneers anticipated. This paper gives an overview of the important things that the standard does; the ways that this has proved to be useful; the importance of standardized descriptions for the components; and some of the reasons why using boundary-scan is not always as delightful an experience as users would like. >