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Analysis by Braille

As a technology, JTAG (or IEEE 1149.1) has been leveraged a lot of ways to do a lot of things that may not have been envisioned when it was first developed. Its original mission, however, was rather simple: provide a way to test whether the board connection between two chips was intact. And, while individual components have a way of describing their internal chains via a BSDL file, according to the folks at JTAG Technologies, there is no such simple equivalent for the entire board’s chain.

So if you’re a simple repair shop without access to full design netlists and such, how do you leverage JTAG to confirm whether the connections on a suspect board are intact?

JTAG Technologies has just announced a product called Autobuzz that will let you establish a JTAG chain baseline for a board that you can then use to test other boards. As the name suggests, it can go through and “buzz” out the connections without really knowing much about the board.

It does this by establishing a reference almost blindly from a known good board in “learn” mode. You can then run the tool in “compare” mode on a board in question to determine whether it matches up.

You do need the BSDL files of the individual components (often available online) and you do need to know the order of the devices in the chain, which may be a bit trickier for complex boards, where you can’t visually inspect the traces, but if you’re a serious shop, you will most likely have access to the board schematic, from which the chain order can be easily deduced.

More info on their press release

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