Good point.  I have only the PICkit2 programmer connected to the MCLR 
pin, so I explored that issue a bit more.

Turns out that the MPLAB allows one to manually set the MCLR pin level 
and that mine was set to "Vil," which is a low logic level. 

Now if I run my "bad" code but tell MPLAB to set MCLR to Vdd, it runs 
correctly and receives characters.  So that solves the problem of why my 
receiver wouldn't work- I was actively resetting the chip with the MCLR 
signal after programming.  (Sure wish they had a visual indicator of 
what the setting was, instead of just two push buttons!)

I still question why, even in the case when MCLR was being asserted, the 
chip ran code and transmitted characters.  Just re-read the spec and it 
says that the PCL register is set to 0 on a MCLR reset.  Seems like that 
should halt execution as long as MCLR was asserted...

Thanks,
Tom


Kevin Jones wrote:
>   
>> (_MCLRE_OFF allows reception, _MCLRE_ON prohibits reception.)
>>     
>
> So basically, you are saying that if you use the internal reset 
> circuitry in the chip you receive ok, if you use an external reset 
> circuit it does not. This would imply to me that your external reset 
> circuit is  faulty or out of spec. What exactly to you have hooked up 
> to the MCLR pin ?
>
> Regards,
> Kevin Jones
>
>
>   
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