PCB

I received the PCBs a few day ago and assembled one PCB yesterday:

I just need a monitor for the PROM.

Monitor Program

The monitor program reads the PORT to determine which program to run:

• PORT 0: Read the PORT to determine which program to run.
• PORT 1: Program 1 -> 8 bit binary counter
• PORT 2: Program 2 -> Return to Monitor
• PORT 3: Program 3 -> Return to Monitor
• PORT 4: Program 4 -> Return to Monitor
• PORT 5: Program 5 -> Return to Monitor
• PORT 6: Program 7 -> Return to Monitor
• PORT 7-F: Return to Monitor

I have only one program at the moment, an 8 bit counter that uses memory address 0 for the low nibble and address 1 for the high nimble:

Update to LogiSim

The LogiSim model has been update to reflect the "As Built" more closely:

And the OpCodes:

Programming Experience

Compared to programming my TTA8 or SubLEq, this machine even with only 4 bits is a dream as the code density is so much higher (i.e. the number of bytes of code to perform an instruction, such as ADD). As instructions are one clock rather than eight clocks, it is also much faster.

What was I thinking when I designed the TTA8 or SubLEq!

AlanX