Introduction to JTAG

JTAG is a technology which is in its third decade as an industry standard. However, its potential as a testing and programming tool is only just beginning to be fully realised.


Connection testing and In System Programming (ISP) are the two applications most commonly associated with JTAG. However the technology has far more to offer.

Non-JTAG-compliant sections of a circuit can be tested by using the interconnecting nets between the devices in the JTAG chain and other devices in the circuit.

XJTAG has been designed to unlock the potential of JTAG, with its development system of software products and JTAG controller hardware (available with a range of connectivity options).

what is JTAG?

What is JTAG?

And how can I make use of it?

JTAG Introduction, Background, JTAG Connection Testing, In-system Programming

High-Level Guide to JTAG

See what JTAG can do

JTAG Technical Overview, TAP signals, Boundary Scan Instructions

Technical Guide to JTAG

A low-level look at how JTAG is implemented

Design for Test techniques

Design for Testability (DFT) Guidelines

Suggestions for improving PCB testability

circuit design, development, manufacturing, service

JTAG Testing with XJTAG

XJTAG extends the possibilities of JTAG

History of JTAG

Advances in silicon design such as increasing device density and, more recently, BGA packaging have reduced the efficacy of traditional testing methods.

In order to overcome these problems, some of the world’s leading silicon manufacturers combined to form the Joint Test Action Group. The findings and recommendations of this group were used as the basis for the Institute of Electrical and Electronic Engineers (IEEE) standard 1149.1: Standard Test Access Port and Boundary Scan Architecture. This standard has retained its link to the group and is commonly known by the acronym JTAG.

Using JTAG

For a device to be JTAG compliant, it must have an associated BSDL file which describes the implementation of JTAG in that device.

A platform-independent way of representing test sequences to be sent through the JTAG chain is SVF.

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