TTi (aka Thurlby-Thandar Instruments) is a well established UK test and measurement supplier who develop and manufacture in-house a range of bench PSU’s, Functions Generators and RF/EMC test equipment.
One particular design utilises an NXP LPC2468 microcontroller in a 208 ball FBGA package that interfaces to a discrete flash memory of type M29W800 in a TSOP48 package. The design engineers at TTi contacted the JTAG Live support team, when it was found that some faults on this design had become difficult to resolve with conventional (functional) test means.
According to a senior design engineer at TTi:
“We suspected that manufacturing faults were occurring on the micro to flash interface section as a small number of boards had failed our existing functional test but we had difficulty in pin-pointing precisely where the problems lay. The obvious solution was to use JTAG/boundary-scan to access the pins of the LPC micro and send simple test patterns to the flash via the boundary-scan register. The trouble was finding a tool which would:
- Not take up too much development engineering time
- Be easy for the production testers to use
- Not cost an “arm and a leg”
“After checking the specifications we bought a JTAG Live controller cable and the Clip package and it worked almost exactly as we hoped, after some minor teething problems. Selecting the correct BSDL model communications to the device was very straightforward and after deciding on the best and simplest set of vectors for our needs, setting up was a fill-in-the-blanks process – no coding was needed with Clip.”
“The system is now installed on the shop floor and if the flash interface on this board type fails functional tests the production test team can use JTAG Live Clip to pin-point a fault more precisely simply by probing the pins on the flash device and checking for stuck high or low indicating an open circuit or a corrupted waveform indicating a short.”
The engineering team at TTi add “The JTAG Live range offers a great introduction to JTAG testing with a minimal investment. We also know that if our needs expand we can upgrade from Clip to the Script package which could add the power of the Python programming language to our boundary-scan testing”.