I'm curious about how to access certain pins of the C64 User Port.  Going
by the pinout here:

https://www.c64-wiki.com/wiki/User_Port

I see there are some pins I'm not familiar with.


4       CNT1	Counter 1, from CIA #1
5	SP1	Serial Port 1, from CIA #1
6	CNT2	Counter 2, from CIA #2
7	SP2	Serial port 2, from CIA #2
8	/PC2	Handshaking line, from CIA #2
9	ATN	Serial attention in
...
B	/FLAG2	Flag 2
...
M	PA2	PA2


I have a basic idea what the counters are for but I'm looking for more
detailed information on all of those pins.

Are there any programming and/or schematics out there that indicate how to
use them in various projects?

Thanks

--- SoupGate-Win32 v1.05