Olin Lathrop writes:

>Read the data sheet.  The maximum voltage for the open drain output is well
>specified.

Thanks for taking the time to post that helpful answer.

I have the 16C71 datasheet here. Maximum voltage on RA4 is 14 volts, same
as MCLR. The original question was regarding the 16F84. The data sheet for
the 16F84 still specifies 14 volts for MCLR but ignores RA4 completely, and
says the max voltage on any pin is VDD plus 0.6 volts. That is pure
baloney, and what is also pure baloney is the data sheet for the 16F84 is
still marked "preliminary" like any Microchip product still in production.
They don't stop being preliminary until they are discontinued.

I have also tested and used the 16F84 with 10 volts on RA4 with no problems.

So basically I disagree that the voltage on the open drain output being
clearly specified for the 16F84. It is ignored completely. Electrical
specifications have always been a weak spot for Microchip.

Cheerful regards,

Bob Blick

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