I have an application that needs 10 I/O lines and I was looking at the
16C505, which has 11, including multiplexed MCLR and OSC pins.

From the data sheet it seems clear that I can easily use the MCLR line as a
data line without worry, since I don't have a hardware reset button and
would only tie MCLR high anyway, but I'm not completely sure about the OSC
pins.

My 99% guess is if I'm using a crystal (or certain other add ons) then I
don't get I/O on those pins.  Is that right?

If so...(this is where I have to go back and read the manual but I'll ask
just in case anyone knows offhand) my timing isn't critical, I just use
crystals because it's habit (or design inexperience).  What is the story on
that INTRC, the internal 4MHz oscillator?  Coincidentally my code is
optimized with delay loops for a 4MHz crystal already, so if I wanted to use
the 16c505, can I just turn on this internal RC and gain use of the OSC pins
as I/O, and have a securely running 4Mhz chip?

I'll be distributing products from this so that's why I wanted to be sure if
I go and try using the RC, it will work longer than the first day I test it
out...

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