James Stanley - SCAMP is alive

I have reached a good milestone on the SCAMP hardware: it can now execute code! It runs all the way through the test program correctly.

The card cage helps to hold the cards in place, and to avoid bending the pins when unplugging them. I also anticipate that it will simplify the construction of the case, because the case won't need to hold the rails. Unplugging the ALU is still pretty hard, because it is plugged into 120 pins.

I still haven't made a clock, so for now the CPU is being clocked by a short Arduino program. I've gone up as high as 10 Hz without observing any instability. I don't yet have any way to infer the state of the machine without looking at the LEDs, so if it went any faster than that I wouldn't even know whether it was working or not. Next steps are to make an adjustable 555 timer-based clock, and interface with the 8250 UART.

The test program just outputs the numbers 0 to 24 to the device at address 0. Each number is generated differently, and tests different things, starting off by just sticking the number in the x register and outputting that, followed by addition, subtraction, bitwise shift, bitwise logic, stack manipulation, unconditional jump, conditional jump, looping, relative jump, and function calls.

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