On Mon, 15 Dec 1997 19:33:10 -0700, you wrote:

>>
>>In a message dated 15/12/97  20:52:46, you write:
>>
>><<
>> The open-collector output pins (e.g. RA4 on 16C84) are not clamped to VDD,
>> and can safely take a voltage above VDD; one of the Microchip guys quoted
>> 14 volts.  >>
>>As this pin doubles as the Vpp does this not force the pic into program mode
>>at 13v and stop program opperation if so it would be unwise to use this pin in
>>this mode of opperation unless you want to write self modifing code ???
>
>I'll have to double check, but I'm positive that the VPP pin / program mode
>pin is MCLR, not RA4.  As far as RA4 and higher voltages is concerned, a
>Microchip FAE has repeatedly told me that it is OK up to about 14 Vdc.
I think the reason RA4 hasn't got a diode is that a high voltage input
is used for factory testing. I'd be wary about using it at >Vdd in a
product, as it's an undocumented feature, which might flip the chip
into some funny mode!
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