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'[PIC]: RS232 voltage levels'
2000\11\01@131228 by Barry Gershenfeld

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>>> There is also a requirement that when the input is open circuit
>>> (i.e. the plug has been pulled out) the receiver chip should
>>> behave as though it is receiving a constant mark signal. This
>>> stop your processor getting continuous interrupts due to an
>>> inadvertent break condition  ;)
>
>Ok, I am prepared to say I may have it wrong, but I was always under the
>impression that this was so, and it makes good engineering sense to do it like
>this. can you imagine the performance of your PC if it was handling continuos
>break characters???

and

>Somebody better tell motorola that the chips they've been making for the
>last 25 years + won't work.. :)

We have to keep in mind that we are discussing the Specs and not
real life.  If you used those Motorola chips all your life you
might design something that worked fine in your world but
suddenly got strange on other people's equipment.  Then the
usual arguments would ensue about whose hardware was working
correctly...and you'd eventually have to get back to the Spec to
explain why one is "more right" than the other.

The "pullup" or "default Mark" is a good idea even if the Spec
doesn't force it on us.

I don't think RS232 even tells you what connector to use, but
we all "know" the answer anyway.

Barry

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2000\11\01@140034 by Bob Ammerman

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----- Original Message -----
From: Barry Gershenfeld <.....barryKILLspamspam@spam@ZMICRO.COM>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Wednesday, November 01, 2000 1:02 PM
Subject: Re: [PIC]: RS232 voltage levels


> >>> There is also a requirement that when the input is open circuit
> >>> (i.e. the plug has been pulled out) the receiver chip should
> >>> behave as though it is receiving a constant mark signal. This
> >>> stop your processor getting continuous interrupts due to an
> >>> inadvertent break condition  ;)
> >
> >Ok, I am prepared to say I may have it wrong, but I was always under the
> >impression that this was so, and it makes good engineering sense to do it
like
> >this. can you imagine the performance of your PC if it was handling
continuos
{Quote hidden}

Yep: Just ask IBM - A 9-pin "D" connector,
or ask Apple - Some funny mini-Din thing,
or ask DEC - a 'modified modular jack' (MMJ)
or ask ...

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Quote hidden}

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