There’s a saying: the more things change, the more they stay the same. Several years ago, we published one of the first tutorials on a new proposed standard for embedded instruments, IEEE P1687, perhaps better known as Internal JTAG (IJTAG). When we published a first edition of our IJTAG tutorial, there was a ‘P’ associated with ‘1687,’ because the proposed standard was still being developed and the document was considered a project draft. Hence the ‘P.’ Now that the project has secured recommendation from the IEEE-SA Standards Review Committee (RevCom), we’ve taken a major step toward removing the ‘P,’ requiring only IEEE-SA Standards Board action to be finally approved. In any event, the timing of a new and completely revised IJTAG Tutorial based on the latest changes and updates in the final draft document is opportune, to say the least.
You might be wondering what has changed in the proposed standard over the last few years since we published our first tutorial and how have those changes affected the second edition of the tutorial. In general, the objectives that were defined when development of IJTAG began have not changed a bit, but several hardware updates such as Local Reset and embedded TAPs have been expanded and documentation aspects, that include the two languages, Instrument Connectivity Language (ICL) and Procedure Description Language (PDL), have been fine-tuned. In addition, some of the terminology that the document uses to refer to certain concepts has been altered somewhat. (For example, ‘gateway’ has been changed to ‘separable interface.’) As the new edition of the tutorial states, the goal of IJTAG is still to specify “an efficient management methodology for embedded instruments and enable instrument portability and re-use from one integrated circuit design to another.”
Overall though, the third edition of our IJTAG Tutorial has been greatly expanded to incorporate much more detail on how certain IJTAG functions work inside chips and on circuit boards. The tutorial now approaches 45 pages and includes almost 20 drawings, illustrations and tables of data. It is a must-read for those who are just starting to learn about IJTAG and for those who want more details on the soon-to-be-approved IEEE 1687 standard. Download the IJTAG Tutorial here.