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MIPS Assembly Code - Convert instruction code to binary

  1. Oct 10, 2012 #1
    1. The problem statement, all variables and given/known data

    Write a single line MIPS assembly code as an input through the SPIM simulator console and the program will output a 32 bit MIPS machine code through the console. I'm using PCSpim to write the code.

    An example,

    I input this instruction in the console.

    addi $t0,$t0,1

    and the console outputs.

    00100001 00001000 00000000 00000001

    I'm trying to write it for other instruction codes as well.

    2. Relevant equations

    MIPS Syscall Sheet
    https://www.student.cs.uwaterloo.ca/~isg/res/mips/traps

    3. The attempt at a solution

    la $a0, 8 # string into $a0
    syscall
    move $a1, $a0, 8

    I just need an example for one instruction like using addi as a guide and I can do the rest. Or point in the right direction. I get stuck after getting the input from console. Should I store the "whole" string to one address? I know there are different ways of doing it like taking each character and check it but I'd rather take the whole code through a string.
     
  2. jcsd
  3. Oct 10, 2012 #2

    Mark44

    Staff: Mentor

    The link you gave won't be much help - it's just the MIPS system calls. What you need is the instruction set reference, showing how each instruction is encoded in a 32-bit number. Here's something that might be helpful - http://www.mrc.uidaho.edu/mrc/people/jff/digital/MIPSir.html

    Here's an example from that site.
    ADDI -- Add immediate (with overflow)
    Description:
    Adds a register and a sign-extended immediate value and stores the result in a register

    Operation:
    $t = $s + imm; advance_pc (4);

    Syntax:
    addi $t, $s, imm

    Encoding:
    0010 00ss ssst tttt iiii iiii iiii iiii

    Here's how you read it - going left to right, the first 6 bits are the the code for the ADDI instruction. The next 5 bits are the register you're adding the value to. The next 4 bits are the register in which the sum will be stored, and the last 12 bits are the immediate value (a constant) that gets added to the first register.

    You need to take an input string, such as "addi $t0, $t0, 1" and parse it so that you can set the appropriate bits in the output string of 1s and 0s.
     
  4. Oct 13, 2012 #3
    Say for example, I put a string "addi $t0,$t0,1" in $a0. How do I put the binary form of that on the console? Do I need to make a comparison using function and define the binary form of that instruction using .asciiz?
     
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