CS 2734 Computer Organization II -- Fall 2000

In this laboratory you will be writing C code to break an input MIPS instruction into its component parts. (It is permissible to use C++ or Java for these assignments.)

• Create a new directory for this assignment.

• Use the following function prototype as a starting point. It functions like the Instruction Register in the diagrams in your text. It should be in a separate file, which I called mipsInstrReg.h in my implementation.

  /* mipsInstrReg.h: Instruction Register Simulator header file  */
  void InstrReg(unsigned int IRinstr, unsigned int *op,
     unsigned int *rs, unsigned int *rt, unsigned int *rd,
     unsigned int *sh, unsigned int *ft,
     unsigned int *ai, unsigned int *ta);
  /* InstrReg: Simulate Instruction Register (break instruction into fields)
   * Input: 
   *   IRinstr: input 32-bit instruction
   * Outputs:
   *   op: op code,     bits 26-31
   *   rs: read reg #1, bits 21-25
   *   rt: read reg #2, bits 16-20
   *   rd: write reg,   bits 11-15
   *   sh: shamt,       bits 6-10
   *   ft: funct,       bits 0-5
   *   ai: addr/immed,  bits 0-15
   *   ta: target addr, bits 0-25
   */
  
  
  

• We have given a strategy for doing this assignment in class: Use a mask and a C bitwise "and" operation to pick off the bits of the field, and then right shift them to the zeroth bit position. (Alternatively, you can use two shifts.) You can also refer to Lab 3 for a similar program.

• Note that there is overlap between the fields, that is, some bits contribute to several different fields, which might or might not be needed, depending on the particular instruction.

• Write a testInstrReg.c program to test the program. It should include the header file mipsInstrReg.h. It should read and process a 32-bit instruction (a 32-bit hex number should be input). The output should be the various fields of the instruction, as unsigned ints.

• It is easy to work with hexadecimal numbers in the C language. For reading with scanf, you should use a %x format. The number read should consist of hexadecimal digits, with or without the leading 0x. For writing with printf, you can use a format like %8x or %08x to include leading zeros. The form %#012x will include the 0x at the front, as well as leading zeros.
• The answer form in the disassembly part of Lab 7 shows various machine instructions broken into their component parts, as a first step toward converting them to assembly language. We will be doing this first step.

• You should check off the function with the lab TA. You must hand the source code to the TA before he starts checking off the project.