README

Overview

This code is a simple model of the MIPS Instruction Set Architecture (ISA) implemented in C. This program simulates the execution of a MIPS binary program, providing operations of a MIPS CPU including fetch, decode, and execution of instructions, memory reads/writes, and register reads/writes.

Key Features

1. Memory and Register Definitions: The program defines memory (Mem) of size MEMSIZE and a register file (Reg) of size REGSIZE + 4. Various registers including program counter (PC), status register, and special registers LO and HI are defined for operations.

2. Initialization: The Init function initializes registers to their starting values.

3. Instruction Fetch, Decode, and Execution: The Step function performs one step in the execution of the program, which includes instruction fetch, decode, reading registers, sign extension, ALU operations, memory read/write, register write, and updating the program counter. If any step fails, the execution halts.

4. Memory Dump: The DumpMem, DumpMemHex and DumpHex functions provide ways to inspect the contents of the memory in different formats (decimal and hexadecimal).

5. Register Dump: The DumpReg function allows you to see the current state of all registers.

6. Command Loop: The Loop function provides a command-line interface for controlling the execution of the program, including stepping through execution, viewing register and memory state, and other operations.

7. File Reading: In the main function, an input file is read into memory, which is expected to contain MIPS instructions. The file reading process also handles error checking and reporting.

Usage

To run the simulator, follow these steps:

1. Ensure that you have the necessary input file. The input file should contain hexadecimal values, each representing a machine instruction in the MIPS instruction set. Each instruction should be on a new line.

2. Run the simulator using the following command:

./simulator <input_file> [-r]

Where `./simulator` is the executable built from this code, `<input_file>` is the name of the input file described in step 1, and `[-r]` is an optional argument that redirects all output to stdout, instead of the default behavior which is to output to the console.

Upon running the simulator, you will be presented with a command prompt. The following commands are supported:

- `'g' or 'G'`: Display the control signals.
- `'r' or 'R'`: Dump the register file.
- `'m' or 'M'`: Dump the contents of memory. If followed by two space-separated numbers, it dumps the memory contents between those two addresses.
- `'s' or 'S'`: Step the simulator forward by n steps, where n is an optional argument. If no argument is given, n defaults to 1.
- `'c' or 'C'`: Run the simulator continuously until it halts.
- `'h' or 'H'`: Display the halt flag.
- `'p' or 'P'`: Dump the instruction memory.
- `'i' or 'I'`: Display the size of the memory.
- `'d' or 'D'`: Dump the contents of memory between two hexadecimal addresses.
- `'x' or 'X'` or `'q' or 'Q'`: Quit the simulator.