30 Dec
2002
30 Dec
'02
7 a.m.
On Monday, December 30, 2002, Sellam Ismail wrote:
I'm having a heck of a time figuring out how to
use the CA and CB ports on
the 6522 as inputs. From the documentation I have, it seems the CA port
can be used for one TTL input, and CB can be used as two.
This is probably incorrect for your situation, and remember, I ain't no
hardware guy yet. I wrote some firmware for an 8051 clone, a Dallas DS80C520
(IIRC). It had some pins that could be used as input or output. When using
them for input, it was necessary to write a 1 to the pins before reading
them. I know, I know, this is a totally different chip, but just maybe your
situation is similar. The reason for the write had something to do with the
way the I/O pins were built, electrically.
--
Jeffrey Sharp