More frustrations today. Nothing seems to work when using Port B as a source. I broke down are wrote and made an automated program to scan through the possible 3 micro op combanations to preform:
Set Ram to 3
Set Ram to 4
RegA + RegB.
I knew from yesteraday that Source 7 (Data port, Zero) ) would allow me to write to ram. The program I set up would clear all of the Ram contents and the Q register Set ram locations 0 and 3 then try every combination of sources and destinations. It would report back if the results matched.
This did not go well.
After hours of trouble shooting and chip swapping I found the problem. The 5 volt supply off the Arduino was not strong enough for the AM2901 and was being dragged down to ~4 volts.
Powering the AM2901 off of a seperate power supply fixed the issue.