Description
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 review the conversions between
MIPS and machine code.
Getting started
We will use MARS (our beloved MIPS simulator!) throughout this assignment. Feel
free to read the attached documents (MARS Tutorial.pdf, MARS features.pdf) if
you have not used MARS before or forgot about how to use it.
If you did not learn MIPS when you learned assembly language, please feel free to
group with other students who have learned MIPS. You will pick it up easily with
their help.
(Exercise) MIPS ↔ Machine Code
TPS (Think-Pair-Share) activity 1 Paired with the classmate(s) sitting next to
you and perform the following tasks (You are allowed to form a group of three):
1. Record the name(s) of your partner(s).
2. Download “MIPS_Reference_Sheet” from CatCourses. We will need to refer
to this sheet in order to complete all the exercises in this lab.
3. Load proc1.s in MARS and study the code.
4. 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).
5. In true assembly language, every single instruction can be translated into a
machine instruction. How many bits does a machine instruction contain?
6. 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.
7. Now, locate the instruction in line #7 of proc1.s. Let’s 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.
8. Now, let’s 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 MISP 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?
9. Now, let’s take a look at line #17 of proc1.s.
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?
10. Finally, let’s 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. What label and address does this instruction jump to?
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?
(Assignment 1, individual) Conversion in proc2.s
Convert the following line in proc2.s to machine code and then back to MIPS
instructions:
Line #7
Line #14
Line #17
Line #20
You must show all the steps including values of the instruction fields
in order to receive points.
Verify your answers with the Text Segment window.
(Assignment 2, individual) Datapath
Trace through the paths the execution of SLTIU instruction in this single cycle
datapath design. Fill in the appropriate control signal values in the table. If
there are any modifications needs to make it work, draw them in the diagram
and create appropriate control values.
nPc_sel ExtOp ALUsrc ALUctr MemWr MemtoReg RegDst RegWr
0
1
(Signed or Zeros)
What to submit
When you are done with this lab assignments, you are ready to submit your work.
Make sure you have included the following before you press Submit:
• Your answers to assignments, TPS activities in a text file, and a list of
Collaborators.
• Your assignment is closed 7 days after this lab is posted (at 11:59pm).
