> Is there a reason to prefer 7400 series over CD4000 series logic?
If you can find real TTL, yes, I would say so. It's less static-sensitive and it's more tolerant to things like hooking two outputs together by mistake. But note that there are many chips that have more or less TTL interfaces (TTL voltages, TTLish numbers, and in some cases switching thresholds) but are actually CMOS - the 74ALS series comes to mind. Of course, if someone somehow builds CMOS chips with TTL's ESD tolerance, short-circuit tolerance, etc, then great. But that's not what I've seen. /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B