Can someone clue me in on the difference between part numbers differing only with an "A" within the number? For example, MK21FN1M0VMD12 and MK21FN1M0AVMD12. I've examined the product selector page and spent an hour or two comparing the data sheets and reference manuals. Obviously not enough time for a line-by comparison of the docs, but the differences I've seen are details in doc formatting and a few words or sentences of text edits. Also, the product selector lists differences in the number of GPIOs and inclusion of VREF - But the ref. manuals show the parts are the same.
What am I missing?