Question About IC Chips

I sure do. BUT, I didn't post a "line of text". I posted a hyperlink to a site giving pointers as to the do's and dont's of connecting unused pins on IC's. If your newsreader doesn't show a simple and fairly short hyperlink correctly, that's not my fault.

Let's say I have an unused logic inverter gate, and somewhere close to it an output which is running at 10MHz.

If I tie the input of the unused gate to the output of the clock signal the earlier unused gate will now run at 10MHz, consuming a lot of power which is wasted. So it is better to tie the unused input to ground or Vcc, which will lock it at a steady state, which will waste a minimum of power.

Oh go have a drink for christ's sake.

I tend to agree with John Fields on this one, mostly because a lot of my work has had stringent budget constraints. A suitable compromise would be to attach notes to the schematic and code (eg SFR values) pointing out the steps taken and the potential ramifications.

A far more likely scenario is that the software doesnt work properly in the first place. Hardware that cant tolerate software going apeshit is a definite cause for concern.

AFA SFR bit-flipping is concerned, the paranoid programmer re-loads SFRs every interrupt, just in case. This precautionary measure, unlike using resistors, costs only a tiny amount of development time; unit build cost is zero.

Cheers Terry

More specifically, what part of that long text are you referring to, and why?

Do you know how to select, copy and paste a line of text?

--- Heh... Like what you say matters? ALL the stuff I get paid for works, my clients are happy campers, and when they want modifications or changes, guess what? They call _me_ because they know the work will be done carefully and properly.

You, on the other hand, seem to blithely advocate the blind peppering of pullups everywhere, whether they're needed or not, just because that gives you the warm fuzzies. Pure waste and idiocy as far as I'm concerned.

Just for grins, think about this: Say that you've designed a piece of equipment using Pinkerton's Rule, (which mandates that pullups be hung from every possible port) and that even though it wasn't designed to operate in a high-EMI environment, it nonetheless finds itself in one.

Now, depending on the locations of the pullups and the length of trace between them and their associated ports, the pullups could do more harm than good. So now, by not having considered the possibility that your equipment might be taken into a high-EMI environment and then, during the design, taking whatever measures necessary to make it immune from EMI you must admit that you didn't execute the design properly and, therefore, come to the conclusion that you are a bad designer.

-- John Fields Professional Circuit Designer

Oh come now, surely you jest.

Your post was specifically related to tying unused inputs to some logic level or other and I added to your post with a link which starts with the header "What should I do with pins I am not using?" If this isn't self explanatory then I feel sorry for you.

As you quoted a text from me and answered with a link I assumed you wanted to reply to what I said, maybe tell me I was wrong or comment what I said, so I spent 5 minutes trying to find out what in that text could be taken as a reply to me, so I was rather irritated when I couldn't find any sense in anything.

If you had bothered to write a few words by yourself, like:

"More on this subject: "

you would have saved me a lot of unnecessary work.

As noted, *good* designers allow for what *could* happen to their circuits under sub-optimal circumstances. 'John Fields' filed under 'do not employ'...................

to

result in

fault...

it,

crybabies

You'll have to ignore J.F.'s rants. I caught him leaving out a pullup once, and he got all pi$$ed off at me and cursed me out.

I'll have to keep on him about that. [snip]

He speaks from experience. ;-0

So, you agree that all likely abuses of your design should be taken into consideration before you sign it off. Thanks for your admission that you're an incompetent asshole.

--- Hmm... I don't usually respond negatively to technical corrections unless they're accompanied by a slap, but I do recall that you're usually ready to come across with some smartass remark whenever you think you can get away with it. If such wasn't the case, then I apologize and thank you for the correction.

---

--- See what I mean?

---

--- See what I mean?

-- John Fields Professional Circuit Designer

Speaking of cheesy............................... :-)

Omigod, a smart-arse on usenet.... that'll be one for the record books.

I've pointed out a number of (IMO) typo's in JFs posted circuits, and received only polite replies.

But once he got all bent out of shape, thinking I was deriding the use of a 555 (which I wasnt, leading me to question his reading comprehension).

OTOH he wrote a fabulous waffly story about comparator hysteresis on 14 june 2004, which I printed to a PDF (yay for PDF995) and kept, so I dont have to explain it to others yet again. So he's cetainly not an idiot, but perhaps a bit touchy.

I do wish he and robert (oops, Fred Bloggs) would leave Larry alone though. What a colossal waste of bandwidth, and talent.

Cheers Terry