What logic families are sensitive to slow rise and slow fall times? I find that HC/HCT needs at least a 500ns rise/fall time in an old Signetics user's guide that I have. Does TTL, 4000 series CMOS, and most newer CMOS technologies have specs for minimum rise/fall times? The follow-up question is, is the slow rise or slow fall time on the clock destructive physically, stressing the part (overheating due to latch-up, metastable, linear region operation, etc), or is the spec there to maintain data integrity and predictability. The system level question is, can I use a sinusoidal shaped clock signal for testing circuits prior to shipping?