At 09:17 PM 12/1/2005 +0000, you wrote:
>Hi guys,
>
>I'm trying to use my PIC16F687's Tx port on the EUSART as a dual
>function pin, ie as a connect detect input and as a Tx channel.
>
>So here's the question, what's the maximum safe loading on the Tx
>port when its doing RS232, I'm imagining its in the region of 2mA,
>but I can't find any details on the datasheet, and its seems unlikely
>it would match the 20mA of the GPIOs...
>
>Thanks - you lot are the best....
>
>Ed

Ed:-

The same output buffer is used whether it's sending data or acting as a
general purpose I/O-- just the input to the buffer gets switched by a
2-input mux, as you can see in the block diagram for the relevant pin--
so the DC characteristics are the same.

Note that as someone else has hinted at, safe loading is not the same as
maximum loading to have the output valid 0/1, also note that the pin does not
really "do RS232" since it provides logic-level output (and inverted).

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


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