I AM NOT UNDERSTANDING THE SITUATION WHEN SHOULD I USE "VOLATILE" WITH VARIABLES ???
"Is it required in the following case to declare PortPin as volatile"
I seem to recall some time ago (years ago?) Keil saying that SFRs and their bit objects are implicitly volatile. I could not find a reference to that in an extremely short time searching. I'll try again when I have time.
Yes, I seem to recall that, too!
I also seem to recall not being able to find it (clearly) documented anywhere...