miller@uiucdcs.UUCP (miller ) (01/11/84)
#N:uiucdcs:36100026:000:607 uiucdcs!miller Jan 10 16:41:00 1984 I am trying to add new I/O ports onto my c64 through the expansion port. I want them to look like the user port, only in a different address space. I tried duplicating the hardware (pull up resistors, etc.) and control lines used in CIA 2 out the back of the expansion port. But for the chip select, I used I/O1 or I/O2 instead of CIA2 (which should map into $DF00 or $DE00). Unfortunately, this did not work. I get the handshaking line out the back of the 6526 to flip, but the output data lines stay high. Has anyone ever added extra I/O ports onto the c64 and can offer suggestions? A. Ray Miller