Re: [CAD_CAM_EDM_DRO] Re: Need help with parallel port input design-follow up...

In a message dated 9/15/2003 8:35:40 PM Central Standard Time,
damonfg@... writes:

> I'm nearly clueless on this stuff. Am I right in assuming that a Motorola
> MC14069UB is the same as the 4069 you refered to? (It's what Google found).
> If so, am I right in assuming that VDD should be set at 5 volts and VSS as
> ground? Can I use the PC 5 volt supply?
>

Jeff: The "CMOS Logic Family" of IC's was begun, I believe, by RCA, and they
used CD4000 as their numbering system. CD4011, CD4007, etc. Motorola began
"second-sourcing" the family, but they decided to use their MC1 prefix in
place of the "CD", so a CD4069 becomes MC14069 if made by Motorola. The "UB"
suffix stands for Unbuffered, B-level. This "U" is used mainly on some such
single-input inverters to indicate they are suited for some monostable/astable
applications where buffering would mess "swings" up so that the "circuit on paper"
would NOT work in real life, like it "looks like it should". The earlier
4000 parts had an "A" suffix, meaning they were "good for maybe 12 VDC max." as I
understand things. The "B" means they are good for 15 VDC, and are quite roB
ust, as this klutz-at-the-breadboard can attest. (even more nifty, I often
find, are the 74HCnn family of parts, though they are rated for use on 5 VDC
(6.0 absolute max.). They are as fast as LS, and will SOURCE as much as they
SINK. There are now not only 74HCnn, but 74HCTnn ("TTL inputs OK", that is,
they will accept TTL "HI" logic levels of only 2.4 VDC, for valid output, yet
still output a FULL 4.99 VDC at 20 mA!), 74AHC, etc.---stuff I have NO clue what
is, anymore!

The use of a CD4069 for a parallel-port isolator makes no sense to me! You'd
need TWO of those if you wanted to isolate all-eight lines, and have FOUR
left over! The 74HCT541 is an OCTAL non-inverting buffer which will handle
ALL-eight lines, and the physical pin-layout is ideal for the purpose! If you
determine that your parallel-port has "positive swings" on up around 4 VDC with
little or no load, then use the 74HC541, as that increases "noise immunity" a
little.

The '541 outputs can also drive the "LED-inputs" of opto-isolators, if
necessary, as they have a max. Ic out of 25 mA!

I use a '541 between all my "printer ports" and the machines I build! GOOD
cookie! Jan Rowland



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