7 Dec
2007
7 Dec
'07
9 a.m.
On Dec 6, 2007 6:28 PM, Roy J. Tellason <rtellason at verizon.net> wrote:
I don't know that you'd even have to do much of anything with those. I
can't
recall the specific locations now, but there was a one-line program I
used
to type in to test those ports. Just "Peek"ing two locations and looping
back, it'd give you a continuously scrollign display of a couple of
numbers,
I think 255 and 127 but am not sure any more since we're talking 15+ years
ago. You'd plug a joystick into a port and wiggle it, try the fire
button,
and watch to see if the number changed with each thing you did -- if it
didn't, there was a bad chip in there.
Reading the digital inputs from the joystick ports is indeed just a matter
of reading $DC00 (port 2) and $DC01 (port 1). The question is whether
there's any obstacle to setting the DDR on the CIA to make some of the pins
on the joystick ports digital outputs rather than inputs. I don't know
whether this would work or not, because the joystick pins on the CIA are
shared with the keyboard matrix. I can dig out my Programmer's Reference
tonight and peek at the schematics, or maybe somebody out there just
knows...?