Some game cause the Apple IIe to hang about apple_iie_mmu_iou HOT 2 CLOSED

There seems to be a problem with CASEN_N and EN80_N.

This is a logic analyzer capture of the game ALIENS, with a trigger on the falling edge of EN80_N:
Both captures are without a 80-Col Card present, on an enhanced Apple IIe.
With the ASIC MMU:

With the MMU from this repository:

For some reason, the CASEN_N and EN80_N signals are wrong in the prototype.

from apple_iie_mmu_iou.

Fixed in 5f5cba5

At first, I though that the SELMB_N computation of the emulator schematics was incorrect. So, I re-wrote SELMB_N to be closer to the ASIC schematics. This new implementation is much simpler than the other schematics one, but do not fix the problem described above.

Later, I was convinced that PG2 somehow ended up with the wrong value and started searching through the logic analyzer traces until I found this:

The CPU places $C054 on the address bus to reset the soft-switch PG2, But while the address is crumbling, the MMU momentarily sees $C055 and sets it back.

To fix, the latch enabling that control these soft-switches must be forced HIGH during PHI_1 (i.e. during PHI_0 LOW).

This fixes the problem with ALIENS, Apple IIe Diagnostic v2.1, as well as almost every game. Except "The Black Cauldron" that seems to have an problem. Will open a different issue for that one.

from apple_iie_mmu_iou.