11/23 clock issue

Brent Hilpert hilpert at cs.ubc.ca
Tue Feb 10 01:28:42 CST 2015

On 2015-Feb-09, at 12:16 AM, Holm Tiffe wrote:
> Brent Hilpert wrote:
> [..]
>> Pete clarified your potentially misleading statement. He wasn't "pissing on your feet".
>> Sometimes Holm, attempts at redemption just result in digging yourself in deeper.
> Soso.
> I wrote a statement to how exactly test an 74S240, Pete and you wrote
> other, in this casenot interesting things.
> It seems that the sentence "all was already sayd, but not from me" fits
> well here.
> The sentences from TI are right and known to me, bute none of them applies
> for a functional check of exactly the 74S240 on the M8186 board.
> Connecting the input of the 74S240 wit an R to Vcc to check the High pegel
> is simply nonsense.

Holm, I was going to just drop this, but you've now added yet another misleading statement which needs correction.

You certainly haven't described how to "exactly test" a TTL input, and pulling the input-under-test actively high is certainly not "nonsense". Pulling the input high is well warranted in the context of the OP's situation (which you insist on limiting the matter to), and would indeed be necessary in a complete test of the input.

Active-high and open-circuit for a TTL input are electronically not the same thing and one could well conceive of a fault (such as junction breakdown/short with applied voltage) in which the input behaved as OK when open-circuit, but failed when pulled high.

Add to this that the input-under-test actually is pulled high in-situ (by the oscillator output), it is even more warranted to test it as such to more closely mimic the in-situ operation.
The objective of testing is not just to check that the inverter output follows the input appropriately, but to check the input isn't failing in such a manner as to upset or damage the oscillator output.
More complete testing would check the current flow through the input, which I would have got to with the OP if it had become warranted after further examination.

Your initial comment in this thread was itself an interjection to my response to the OP to pull it high & low. If I had been overly sensitive in the manner of interpreting your comment I could have taken offense, but I didn't, and I didn't argue with it at the time. But as per above, it can well be considered as utterly inadequate even in the limited context for which you claim it was intended.
You have been telling others that their additional commentary and clarifications - presented for more comprehensive understanding for others - are "wrong" and "not interesting" when they have been right and you are the one who has been repeatedly wrong.

If you want - as per one of your messages - allowance for not being a native-English speaker, then you should have earlier taken the hint that your initial comment was incomplete or could be misleading, from the 2 or 3 native-English speakers who responded with clarifications.

But go ahead, dig yourself in deeper.

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