Lab 09: Machine Language

Lab 09: Machine Language

Overview
Since computer hardware can only communicate in 0’s and 1’s, our programs written in MIPS must be
translated into machine code containing only 0’s and 1’s so that they can be executed. In this lab, we will
practice the conversions between MIPS and machine code.
Getting Started
Before we begin any activities, create a directory (Lab_9) inside the CSE31 directory we created in the first
lab. You will save all your work from this lab here. Note that all the files shown in green below are the
ones you will be submitting for this assignment.
You must have a clear idea of how to answer the TPS questions before leaving lab to receive
participation score.
MIPS ↔ Machine Code
TPS (Think-Pair-Share) activity 1: Discuss questions 1 – 6 (50 minutes) while paired with your classmates
assigned by your TA (you will be assigned to groups of 3-4 students) and record your answers in a text file
named tpsAnswers.txt under a section labelled “TPS 1” (you will continue to use this file to record
your answers to all the TPS questions that follow in the lab handout):
1. Download “MIPS_Reference_Sheet” from CatCourses. We will need to refer to this sheet to
complete all the exercises in this lab.
2. Load proc1.s in MARS and study the code. This is similar to compare.s from Lab 06.
3. After assembling the program, study the Text Segment window and see how your source code is
translated into True Assembly Language (Basic) as well as machine code (Code).
4. In true assembly language, every single instruction can be translated into a machine instruction. How
many bits does a machine instruction contain?
5. To utilize the limited number of bits efficiently, all machine instructions are categorized into different
types (or formats). How many types are there? What are they? Give 2 operations for each type as
examples.
6. Now, locate the instruction in line #7 of proc1.s. Let us translate this instruction into machine code.
a. What instruction type is this? How many fields does this type of instruction have? What are the
names of these fields?
b. Refer to the MIPS sheet, what is the value of the opcode of this instruction in hex? What register
is rs? What is the value of this register in hex? What register is rt? What is the value of this register
in hex? What is the value of immediate in hex?
c. Construct the machine code of line #7 using the values obtained from part b. Write your answer in
both binary and hex formats. You can verify your answer with the Code column in Text Segment
window.
7. Now, let us convert a machine code to a MIPS instruction. Locate address 0x00400010 from the Text
Segment window.
a. What is the machine code at this address in hex? Convert this code into binary.
b. From the binary version of this machine code. What is the instruction type? How can you tell? How
many fields are there in this instruction type? What are the names of these fields?
c. According to the binary machine code, what is the value of each field in hex?
d. Refer to the MIPS sheet, what operation is this instruction? How can you tell? What is the mapping
of the registers being used in this instruction?
e. What is the final MIPS instruction? Is it the same as the Source Column in the Text Segment
window?
8. Now, let us take a look at line #17 of proc1.s.
Lab 09: Machine Language
CSE-031-01 Points: 20
a. What format is this instruction?
b. What are the values of opcode, rs, and rt of this instruction in hex?
c. What is the name of the target label if it takes the branch? What is the address of this label in hex?
(Hint: you can find it in the Text Segment window.)
d. So, do we put this address as the value of the immediate field of the instruction? Why?
e. How do we find the value of the immediate field? What is this value?
f. What is the machine code of this instruction in binary and hex formats? Does your answer match
the Code column in the Text Segment window?
9. Finally, let us convert the j instruction in line #20.
a. What format is this instruction? How many fields are there in this format?
b. What is the opcode of this instruction in hex?
c. To what label and address does this instruction jump?
d. How many bits can you use in the address field of the instruction? How can we “squeeze” the
address into this field? What are the reasons behind this approach? What is the value of the
address field in binary?
e. What is the machine code of this instruction in binary and hex? Is it the same as what’s in the
Code Column of the Text Segment window?
Your TA will “invite” one of you randomly after the activity to share what you have discussed.
Individual Assignment 1: Conversion in proc2.s
Convert the following line in proc2.s to machine code and then back to MIPS instructions (note your
answers in a text file named individualAssign1.txt):
• Line #7
• Line #14
• Line #17
• Line #20
You must show all the steps including values of the instruction fields when you demo this lab.
Verify your answers with the Text Segment window.
Collaboration
You must credit anyone you worked with in any of the following three different ways:
1. Given help to
2. Gotten help from
3. Collaborated with and worked together
What to hand in
When you are done with this lab assignment, submit all your work through CatCourses.
Before you submit, make sure you have done the following:
• Attached your individualAssign1.txt and tpsAnswers.txt.
• Filled in your collaborator’s name (if any) in the “Comments…” textbox at the submission page.
Also, remember to demonstrate your code to the TA or instructor before the end of the grace period.