You’ve heard all about IJTAG (IEEE P1687) [1,2,3], a new standard for accessing embedded test and 
debug features that makes it easier to integrate IP blocks and to retarget hierarchical (test) patterns [4,5]. You may also have heard that IJTAG is compatible with JTAG. The question now is what this means for your future test methodology. Can you use IJTAG on designs that use an in-house solution based on IEEE 1149.1 top-level test access and IEEE 1500 compliant cores? Can you try out IJTAG without any hardware changes?

The answer is yes. You can use P1687 on 1149.1/1500 compatible designs, without changing your hardware, and still reap some of the key advantages of IJTAG, such as automated test-pattern generation for any level of your product’s hierarchy. Here’s how.

Start with what you have

Say you have a design with a top-level 1149.1-compliant test access port (TAP) controller and a 1500-compliant wrapper TAP (WTAP) for each core (Figure 1), connected in any valid configuration. Assume that the embedded IP (IP1 through IP6) does not comply with the P1687 standard. This means that you cannot use P1687 to describe patterns directly at the IP level and have them automatically retargeted to the top level.