Phil WrightI finally got some free time over Xmas to test out the register store board. It needs to store 32 bits so I use 4 x 74HC574 in order to store the value for output on port A and then another 4 to store the same value output on port B. So the value is stored twice but always updated together on the write line going high. Because the '574 has buffer out lines it means we end up not needing any separate buffer drivers. Remember that there will be 16 registers all connected to the port A and B and so we can only output when the specific register is selected.
The left board is the register store and the right just a simple bus board used to distribute values and power. Now I need to order some for '574 chips so I can build out the other 14 that I need.
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Your parts are widely spaced, I thought you'd need to make a more compact system...
Something else occured to me : you'll need to drive 16×2=32 data inputs. That's a big "fan-in" so each board should at least contain a simple buffer, or your system will be slow because of all the capacitance on the bus lines...
This is why I organised the #Discrete YASEP in "pages", and used multiplexers, to reduce the load on the read and write buses.
BTW do you use careful layout for the connexion wires ? beware of crosstalk :-)
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