Bob,
     I appreciate this. I always use resistors even in plans that show=20
no resistors. I just felt that I should and now I am glad that I have=20
done that. Using worst case resistances you are looking at 83 mA to=20
167mA. The pin won't last long at that current draw. Yep it is  good=20
that the engineer didn't put it in writing. I learned something new. It=20
has been a good day.
Thanks,
rich!

On 7/3/2014 6:57 PM, Bob Blick wrote:
> There is no current limiting on PIC pins. The internal resistance is=20
> such that driving something like an LED won't kill it right away, if=20
> the LED is tied to ground (it's using the P-channel output MOSFET). It=20
> is a bad idea, though. With a five volt supply on something like a=20
> 16F877 the internal resistance of the N-channel output is 30 to 50=20
> ohms and the P-channel is almost twice that. So if you tie an output=20
> pin to +5 and write a zero to that port it will try to pull 100mA=20
> through that one pin and it will die soon. This is just from memory,=20
> but I did test it about 10 years ago after a Microchip field engineer=20
> said it was OK to drive LEDs without resistors from a PIC. Smart guy,=20
> he didn't put it in writing :) Best regards, Bob=20

--=20
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