>> The datasheets is DS30081F page 21: (quote) 'Note: I/O pin has protection
 diodes to Vss only.'
>> I just tried measuring a device, and the datasheet is ofcourse correct. Only
 a
>>  diode to Gnd (Vss) can be measured.
>> One of the advantages of an O/C (or Open Drain) output is that you can switch
>>  between Gnd and a voltage higher than Vcc.

>Woah boy.  Just remember that you are not talking about a ULN2003 relay
driver here.  The PIC16C/F84(A) could be inadvertently be put into
Probramming mode if you pull the _MCLR pin too high (especially
when Vcc is low)  If you must have a 6V open collector output
from say a set of batteries and you know that you chip will
reset correctly (open collector reset IC connected to _MCLR then
you can probably get away with it even if you put a low drop regulator
onto the rest of the IC and run it at 5V.

>If you want open collector at above supply voltage then put in the
transistor and resistor and feel safe.

>Cheers
>Kalle Pihlajasaari     kalle@data.co.za

What are you talking about? We are discussing RA4 here, not _MCLR...