Main (main.py)
This page contains how the main.py file works.
Instruction Set
The 16-bit processor uses binary instructions based on a custom instruction list implemented in the Instruction Module.
Creating an Instruction Set
Let’s generate a small set of instructions to see how it works. The instruction we want to generate:
add 3 to 2 -> store in RAM
INSTRUCTION SET |
A |
B |
C |
D |
|---|---|---|---|---|
Logic or Arithmetic |
0 |
1 |
0 |
1 |
operation code 1 |
0 |
0 |
0 |
0 |
operation code 2 |
0 |
0 |
0 |
0 |
zero replace |
0 |
0 |
0 |
0 |
swap |
0 |
0 |
0 |
0 |
less than |
0 |
0 |
0 |
1 |
greater than |
0 |
1 |
0 |
0 |
equal to |
0 |
0 |
0 |
0 |
a register |
0 |
0 |
0 |
0 |
b register |
0 |
0 |
0 |
0 |
RAM |
0 |
0 |
0 |
0 |
select register ‘a’ or RAM |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
|
0 |
0 |
0 |
0 |
|
1 |
0 |
1 |
0 |
|
Direct write to register ‘a’ or use ALU |
1 |
1 |
0 |
1 |
Instruction A writes the value 0b11 (3 in binary) to register ‘a’
Instruction B tells the ALU to copy the value in register ‘a’ to register ‘b’
Instruction C writes the value 0b10 (2 in binary) to register ‘a’
Instruction D adds the value in register ‘a’ to the value in register ‘b’ then writes the value in Random Access Memory
Note
The address of where to store the value in RAM is determined by the value of register ‘a’
In Python our instruction becomes
instruction_set = [
0b0000000000000011, # set a_reg = 3
0b1000001000001001, # set b_reg = a_reg
0b0000000000000010, # set a_reg = 2
0b1000010000000001, # set ram(a_reg) = a_reg + b_reg
]
Main Process
To show that the instructions work I’ve created a simple computer to run the instruction set. This involves connecting the Control Module, Instruction Module, Program Counter, Unified Memory and clock-cycles together.
The main method in the Computer class in main.py will follow these steps (based on clock cycles):
Load the current instruction into memory
Run the calculation process on the bits
Write the output into memory
Increment the program counter
The rest of the code in the main.py file is boilerplate needed to run the instruction using Python’s generator functions.