eslapion wrote:It's the opposite.
The MOS6522 IRQB can only drive low or do nothing at all. The 65C22 or R65C22 can drive low or high. This way you can connect more than one 6522 to the same IRQ line and this is done in many pieces of equipment. If a 6522 pulls low and a R65C22 pulls high then you have a tug of war between the two.
A diode may do the job but it has to be extremely fast and have a very low voltage drop. The 1N6263 I use on the Behr-Bonz DRL 'AND' gate should to the job.
A 10kOhms pull-up resistor will definitely not.
Thanks Eslapion. I didn't have that diode, but I managed to get it to work with a 1N5814:
At least the R65C22 works for my Vic-20 and its keyboard. Unfortunately it didn't work for the IEEE device. I got the same problems as with the MOS 6522. E.g. "Load"$",9" loads the directory but displays nothing (unlike the original Vic-1112 which shows it):
I will test more another day. Maybe there is a strange bug in the software or something about the R65C22 in this configuration.