Figure 1: Writing bytes to LCD registers.
Figure 2: LCD seems to work (and so my buffered I/O expansion bus).
Here is the electrical diagram:
Figure 3: LCD interfacing.
Figure 4: MKHBC-8-R1 setup with main CPU board, I/O expansion buffer, UART and LCD.
Thus I confirmed that both my I/O address decoder and buffered I/O expansion bus work by having 2 peripheral devices connected to the I/O bus and working without any conflicts.
The whole thing becomes a monster of bread boards and wires. In fact I start to run out of both. I think it is time to start assembling this thing on more permanent prototyping boards. I will use point-to-point soldering method. It is a lot of work, but I have lots of magnet wire, solder and prototyping boards.
Done for today. Thank you for reading.