LCD's have very generous timing, but they're slow, and, for the MMIO approach, 805x's are quite stingy with active nRD and nWR time.

If you take your time, you can easily "talk" to an LCD, but if you're to fast, they won't "hear" you.

This is the very reason for many of the LCD posts we see, the ancient designs do not work with todays faster processors. If a design worked or maybe "worked" with a 12MHz 12 clocker, it, very likely, will fail with a 6 clocker or a higher osc freq unless changes are made.

Erik