kenasw@btinternet.com wrote :

> Why does pc com port use RS232,...

To be able to communicate with *other* equipment with
serial (RS232) ports, of course.

> is there a standard that requires this.

Yes. And guess what,  the standard is called "RS232"...

> On the other hand, why do the pics use uart without rs232,  is this
> a pic problem which will make it more complex to connect to pc?

Very few (if any at all) uart's has RS232 builtin. Today the RS232
interfacing is done with chips like the MAX232. Earlier (say more
then 10 years ago), one had a separate +/- 15V power and simple
"RS232-drivers". The MAX232 generates the +/- 10-15 V internaly.

But why not just google around on the net or check your local
library. There have been a lot of books written on serial
communication over the years. I'm not sure of how old the
RS232 standard is, but at least as old as I've been in the
business, about 25 years. So it pre-dates most of the
technology we use today.

Jan-Erik.



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