20 Jun
2015
20 Jun
'15
6:14 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Mouse
Sent: 20 June 2015 13:54
To: cctalk at classiccmp.org
Subject: Re: OT: learner kits (was: Re: using new technology on old
machines)
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 more tolerant to things like hooking two outputs
together by mistake.
The pack recently mentioned was, I think 74LSxx TTL which is probably the
most common and should in most cases be capable of replacing standard TTL.
The other advantage of TTL is that is quicker. On the other hand CMOS is
more tolerant of supply voltage.
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.
Most modern CMOS is "BE" series and so have ESD protection.
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