CAPC - Part 9

The ALU Unit
I combined my ALU combination circuit with 3 16-bit registers to create the ALU unit, and then wired the various register controls to the signal bus.

The ADD Instruction
Next, I created the operation logic for the ADD instruction inside the OpLogic device.

Finally, I spent an hour fixing everything that was broken. I placed two of the registers in backwards, I misnamed an output wire in the OpLogic device and the ALU combinational circuit was malfunctioning. I never figured out why the ALU had malfunctioned. I disconnected it from the processor and hooked it up to hex displays and keyboards and saw that it was indeed failing. Then I rebuilt another one beside it that was exactly the same and was dumbfounded to see that it did work while the identical one beside it didn't.

I gave up on trying to figure it out and simply copied and pasted the working one back onto the processor after which my ADD instruction worked beautifully. I ran these two test programs while working on it:

ADD Test Program
FFFF 6009 700B 600A 700C 100B 700D 0000
0000 ABCD 1234 0000 0000 0000

Simpler ADD Test Program
6004 1005 7006 0000 1111 2222 0000

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