salimtirit / assembler-and-compiler

Assembler and compiler for a hypothetical CPU with python

Assembler and Execution Simulator

This project consists of an assembler and an execution simulator for a hypothetical CPU called CPU230. The assembler translates assembly code written in a high-level language into machine code that can be executed by the CPU230. The execution simulator, on the other hand, takes the machine code and simulates the execution of the program step by step.

CPU230 Architecture

CPU230 is a simple CPU that has the following architecture:

Each instruction has a fixed length of 3 bytes with the following format:

Opcode (6 bits)	Addressing mode (2 bits)	Operand (16 bits)
6 bits	2 bits	16 bits

The addressing modes are as follows:

Addressing mode bits	Addressing mode
00	Operand is immediate data
01	Operand is given in the register
10	Operand’s memory address is given in the register
11	Operand is a memory address

Registers are represented as bit patterns, given in hex:

PC=0000, A=0001, B=0002, C=0003, D=0004, E=0005, S=0006.

Instructions

The following instructions are supported by CPU230:

Instruction	Instruction code (hex)	Operand	Meaning	Flags set
HALT	1	-	Halts the CPU.	-
LOAD	2	immediate / memory / register	Loads operand onto A.	-
STORE	3	memory / register	Stores value in A to the operand.	-
ADD	4	immediate / memory / register	Adds operand to A. Perform the addition by treating all the bits as unsigned integer.	CF, SF, ZF
SUB	5	immediate / memory / register	Subtracts operand (OPR) from A. Implemented as ADD instruction as follows: A - OPR = A + not(OPR) + 1	CF, SF, ZF
INC	6	immediate / memory / register	Increments operand (equivalent to add 1)	SF, ZF, CF
DEC	7	immediate / memory / register	Decrements operand (equivalent to sub 1)	SF, ZF, CF
XOR	8	immediate / memory / register	Bitwise XOR operand with A and store result in A.	SF, ZF
AND	9	immediate / memory / register	Bitwise AND operand with A and store result in A.	SF, ZF
OR	A	immediate / memory / register	Bitwise OR operand with A and store result in A.	SF, ZF
NOT	B	immediate / memory / register	Take complement of the bits of the operand.	SF, ZF
SHL	C	register	Shift the bits of register one position to the left.	SF, ZF, CF
SHR	D	register	Shift the bits of register one position to the right.	SF, ZF
NOP	E	-	No operation.	-
PUSH	F	register	Push a word sized operand (two bytes) and update S by subtracting 2.	-
POP	10	register	Pop a word sized data (two bytes) into the operand and update S by adding 2.	-
CMP	11	immediate / memory / register	Perform comparison between A-operand and specified operand and set flags accordingly	SF, ZF, CF
JMP	12	immediate	Unconditional jump to specified address	None
JZ/JE	13	immediate	Jump to specified address if zero flag is true	None
JNZ/JNE	14	immediate	Jump to specified address if zero flag is false	None
JC	15	immediate	Jump to specified address if carry flag is true	None
JNC	16	immediate	Jump to specified address if carry flag is false	None
JA	17	immediate	Jump to specified address if above (unsigned comparison)	None
JAE	18	immediate	Jump to specified address if above or equal (unsigned comparison)	None
JB	19	immediate	Jump to specified address if below (unsigned comparison)	None
JBE	1A	immediate	Jump to specified address if below or equal (unsigned comparison)	None
READ	1B	memory / register	Reads a character into the specified operand	None
PRINT	1C	immediate / memory / register	Prints the specified operand as a character	None

Memory addresses can be given as [xxxx] or r, where xxxx is a hexadecimal number or r is a register name. Labels can also be used. A label marks the address, xxxx, at the point it is defined. Wherever you use a label, you should substitute the marked address xxxx for the label.

Note that when you add two n-bit numbers, you can get 1+n bits as a result. You store the leftmost (most significant) single bit in CF. You store the other n bits in the destination location. In this project, n is 16 bits.

Execution

The execution part of the project involves running the binary code generated by the assembler. The assembler is called "cpu230assemble" and the execution simulator is called "cpu230exec". Here are the steps to use these programs:

1. Save the assembly code in a file with the extension ".asm". For example, you can save your code in a file named "prog.asm".

2. Open a command prompt or terminal and navigate to the directory where your ".asm" file is located.

3. Use the following command to assemble your program and produce the binary output:

cpu230assemble prog.asm

This will generate a binary file named "prog.bin" in the same directory.

4. To execute the binary file, use the following command:

cpu230exec prog.bin

This will run the binary code and produce the output specified by your program.

The above process is illustrated in the example below:

Note that you may need to provide additional arguments to the assembler and execution simulator depending on the specific requirements of your project. Please refer to the project specifications for more information.