Simpletron

From the apprentice Lab 10.10 (maybe).

The requirements given are as follows.

However I have also added in a stack which grows up from the bottom of the memory. I have also added a call and return opcode and a memory dump opcode for debugging, and added instructions to implement a simplistic printing function.

New Instructions

Instruction	Human Readable Description
12xx	WRITE the Accumulator contents to stdout
22xx	PUSH the Accumulator to the stack
23xx	POP from stack to accumulator
24xx	CALL subroutine at the memory location currently in the accumulator. The current programCounter is pushed to the stack
25xx	RETurn from subroutine to the memory location popped from the stack.
99xx	DUMP memory to stdout
50xx	LOAD Literal xx into accumulator
51xx	LOAD from Address in accumulator, into the accumulator

Considerations

1. The CALL and RET instructions rely on the programCounter to be the next item in the stack. Each subroutine must therefore ensure that there is a POP for every PUSH performed.
2. The 100 words of memory are not used to hold the program code, there is a separate program memory for this.

Build and Run

The project uses cmake, so to make use:

> mkdir build
> cd build
> cmake ..
> make

To run tests:

make test

To run as normal:

> ./src/simpletron

To enable debug messages run with debug as the argument

> ./src/simpletron debug