CS 2734 Computer Organization II

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 the Instruction Register simulator. It should be in a separate file mipsInstrReg.h.

  /* 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
   */
  
  /* dumpInstrReg: print the values returned. */
  void dumpInstrReg(void);
  /* Requires storage within the implementation file for the different
   * fields.
   */
  

• We will discuss 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.)

• 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, but then will be simulating the actions of the MIPS computer on these components.

• 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.