Information from and communication between board developers and test developers is key to creating a successful boundary scan application…and, to saving time and money.
In fact, we advise the board developer certify that boundary scan tests can be enabled and operate with a specific procedure. A way to certify that boundary scan circuits can be controlled and accessed for basic boundary scan operations is to use a commercial boundary scan test tool. (Of course, onTAP comes to mind.)
Not every boundary scan application experiences delays—some applications come right up and run without any problems. But when there is a delay, oftentimes that delay can be traced back to lack of information from the board’s developer to the board’s tester. Any setup conditions required to bring up a board should be clearly documented.
When passing on a board for test, it is important that the test developer knows:
• Setup conditions on a board that have to be maintained before and during tests. In some cases, a sequence involving multiple steps is required to control the voltage levels on a board—for example, voltage control and watchdog timer signals that may need to be guarded.
• The boundary scan register pins are controllable. This can be done using a boundary scan test tool to create an interconnect test. Debugging the test isn’t necessary at this point because your goal is to use the interconnect test to verify that the boundary scan register pins can be controlled.
It is also very important the board tester has the correct BSDL files. The developer is in the best position to provide the correct set of BSDL files because sometimes only they have access to them from their supplier or the BSDL files may be proprietary. But just as importantly, the developer knows which files best match the devices on the board.
While these are a few simple steps that can be taken, they are very big steps in terms of saving time and money once a board has been passed along for test.