ELA Board Info
From stuff I previously posted, and some memories, I think that this is what the logic on the ELA board does. You can find the PDFs for these on my page that I mentioned earlier. This is pretty much in order from when the EIGHT mainboard wires hit the ELA board.
HD74HC14
It evens out the "clock" line. If I recall correctly, there's like a GND, +5, LATCH (or clock), and some input lines. This LATCH line may change from on to off, but we don't want weird things happening while it's changing, so I think I remember that this chip would even it out, so that it's either ON or OFF and nowhere inbetween.
HD74HC174 (latches the input)
When the latch/clock line changes (I don't remember if it goes low to high or high to low) then, it's time to look at what's on the input lines. I'm trying to keep this simple for the non-engineers out there. Immagine if you had a combination lock with 3 numbers and you wanted to learn the combination. You wouldn't watch the owner spin the dials and try to guess which combination was right. You would wait until he opened the latch and then look at what 3-digit number was on the lock at the time he opened the latch. This is the same idea. The mainboard sets up the important lines and once it's all set up, it sends a latch signal saying "read the lines now." That's what the HD74HC174 does.
HD74LS138 (decodes the inputs)
This takes 3 lines of input and turns it into 8 lines of output. The idea is that with 3 bits of input, we can count up to 7 in binary. 000-111 If you input 000, then it will turn on output #0 and turn off outputs 1-7. If you input 010 (2) then output #2 would turn on and all the other outputs would turn off. Well, you might be thinking that we only have 6 luminescent panels. So, what? The mainboard just counts from 000 to 101 (5) and never counts past 5, and we ignore outputs 6 and 7.
SN74LS368an
All I remember is that this chip was there to sink current. I'm no electrical engineer, but I guess that the other chips would possibly burn out if they were used by the converter/inverter circuitry.
So, this does not account for all the inputs. I don't recall offhand, but maybe some are unused, or maybe there are some additional voltages that the board supplies.
