Testing it all!
Today I have some time to test, but I haven’t had much time recently at all. I’m going to start off by testing out the registers, which is complicated slightly by the 74hc154’s, but not by much. There’s a lot that I have to make sure I wired right, and while I probably should have started earlier, now’s a better time than never, right?
74hc154 pinout and truth table
For the general purpose registers, going left to right, they’re 10-15 on the 154’s, which means HLHL to HHHH (and using the jumpers, it’s reversed to LHLH ) as the truth table is MESSED UP, where a is the LSB…
So here’s a funny fact I mixed up the order of these decoders, OOPS… so here’s the new order (and this is put in DCBA order, pin order irl is ABCD)
(It’s now been moved to one of the frequently-updated documents here )
Well, I think the registers are all set, which is nice. I don’t think I’m going to test the A&B registers, as well as the ALU right now as I want to setup LEDs for those on a board. (I also don’t have that many jumpers free to view all of those right now.)
I’ll have to start working on that soon, but that’ll mean running a BOAT load of purple LED wires, which will make these boards even less portable than they are.
Well, that’s it for today, hopefully tomorrow I’ll have more time for this. I doubt it, given the hours I want to work and all that. The next best chance will be Saturday evening, or Sunday morning/afternoon&evening.
I think my next target will be to finish the current clock, and start testing out everything else(PC, ALU). I only had a couple errors in the registers module, namely the DIR pin(needed to be 5v instead of ground to get it to go A->B), a wire was in the wrong order for one of the decoders, and the order is messed up. But, that’s not too bad given the literal mess of wires. I might have swapped a bit somewhere, but that’ll take thorough debugging with a completed system, or at least something much further than what currently exists.
It’s also getting closer to the time where I need to purchase a board to start building it all out on, as that’ll get me to the point where I can hook things up to the bus for real, as right now I have 6 completed(ish) modules, and 3-4 more that I need to wire up that will all have to be connected to the bus. And once I have a permanent bus wired up, I can start doing simple things like counting up and down, outputting values to a register, etc. Half of this build will be over-complicated but it’s MY build, so I do it MY way. :-)