Streaming fast access to ADCs and DACs for mixed-signal ATPG

An analog test bus and serial digital access to ADC and DAC parallel ports are two widely used analog DFT techniques. Unfortunately, they cannot be described in a standard way that could facilitate automatic test pattern generation (ATPG). Furthermore, serially accessing an ADC/DAC is typically too inefficient for periodic sampling for various reasons, but mostly because of the capture/update-then-shift sequence used in IEEE 1149.1, 1500, and 1687. This paper shows that if a small amount of digital circuitry is added to each accessed ADC/DAC parallel port, they could be described in IEEE 1687 instrument connection language (ICL) to facilitate optimally efficient streaming access to the parallel ports. Furthermore, this could be automated by adding our proposed “iStream” as a new 1687 procedural description language (PDL) command. We provide examples of how it would be used, along with evidence to show it can provide more efficient (up to 2X, or more) serial access rate to ADCs and DACs than previous automatable approaches.