Designs Nearly Done

Quite a bit of rework and error checking done and more to be done, but I have completed schematics and PCBs for:

1. Mother board and front panel
2. Timing board
3. Program counter and memory address registers board
4. Memory access registers and program counter board
5. ALU board
6. Timer and interrupt board
7. Serial I/O board

All that is remaining is the memory board.

The idea of having so many boards is to make it easier to test the boards (individually) and to redesign them if (when!) required. A smaller board is less likely to have errors than a bigger board.

I dropped the crystal frequency to 4.9152 MHz and removed the first clock divide by two flip-flop. The serial rate is hard wired at 4800 baud. The interrupt service frequency is also 4.8 kHz. To begin I don't need the serial board. Still there are a lot of boards that need to work together before it works.

Sent

After checking the boards (every board except one needed editing), I sent them off for manufacture. I even sent th serial board even though it is a bit premature.

Now to buy the components I do not have.

Parts

I have in the past used 74LS parts but have migrated to 74HC parts. So after checking for parts availablity I have learnt that the 74HC93 is very rare. Basically I should use something else in future.

AlanX