Timing Board

I have added a Timer to the Timing Board. The timer triggers an interrupt every 256 instructions. If I use a 20 MHz crystal fro a 10 MHz clock (the max!), then an interrupt is triggered at 9766 Hz which is close enough to 9600 baud for a serial interface (for later).

I have also moved the interrupt register onto the timing board to free up a bus line for a Serial Clock (SCLK). The timer uses INTR7 (the highest priority) which is not longer accessable from the bus.

Here is the EasyEDA Schematic:

Only three boards remain:

• PC
• ALU
• Memory

Then possibly a Serial Board.

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Modified the timing board for 16x the baud clock as I found a schematic for serial input:

(Source: http://digitarworld.uw.hu/circuits.html).

AlanX