I don't have a lot of knowledge on this topic and everytime I try to understand I got confused ????. So, What is the best way to decode for OPN chips? I am just trying to play around with some of the chips I have.
Here are the 2 options I am going to try:
Option 1:
Using 74LS30:
From cartridge slot directly:
A2 to A6, A7/ (inverse) and /IRIQ (inverse) then output to CS
Option2:
Using 74LS138:
A4, A5, A6, for A, B, C and /A7 (Inverse) for E1. Then E2 or/and E3 iare fed using the following logic:
/WR and /IRIQ fed into 74LS32 that gives output is X1
/RD and /IRIQ fed into 74LS32 that gives output X2
Now: X1 and X2 fes into 74LS08 that gives output fed into E2 or/and E3 of the 74LS138
The output Y of the 74LS138 will be fed to CS of the OPN2
Then we have A0 and A1 directly into the OPN2 chip from the cartridge slot.
