Finished the AB register. It's the same as the XY register minus 16 bit in and out to address bus. I'm getting much better at the wiring. For previous modules I would wire up just enough that I could test it, and then add a bit at a time testing as I went. This time I wired up the entire thing before testing, and only had one mistake when I fired it up (two bits crossed over on A). It was a quick to spot and quick to fix. My productivity should go up now. I've also received all of my orders so I have everything I need to complete the entire system. I dug up my label maker to tag the control lines.