New Techniques for Accessing Embedded Instrumentation: IEEE P1687 (IJTAG)

There is an industry-wide initiative called IJTAG (I for Internal) that has been prompted by the fact that many device and board test engineers are using the IEEE 1149.1 test access port and its supporting hardware and instruction features to access a variety of device-internal instrumentation. The IJTAG initiative was started at ITC 2004 and is now supported by over 50 device design and test professionals from all sectors of the electronics industry. IJTAG was formed to control the proliferation of unusual uses and, in some cases, non-compliant design of the TAP, which culminated in the 2005 submission of a project authorisation request to the IEEE to standardise the new technology emerging from the study. The IJTAG initiative is now known as the IEEE PI687 draft standard for the access and control of instrumentation embedded within a semiconductor device. In the words of the PAR, this standard will develop a methodology for access to embedded test and debug features (but not the features themselves) via the IEEE 1149.1 test access port (TAP) and additional signals that may be required. The elements of the methodology include a description language for the characteristics of the features and for communication with the features, and requirements for interfacing to the features. This embedded tutorial describes the work carried out so far by the P1687 working group. The two presenters are members of the P1687 core group and they will reflect the very latest thinking of the group