CS334: MIPS language _Mars simulator

Lab 2_1

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Contents:• introduction.• Part1:MIPS assembly language.• Questions.

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Assembly Language

Instructions are the primitive operations that the CPU may execute.Different CPUs implement different sets of instructions. The set of instructions a particular CPU implements is an Instruction Set Architecture (ISA).

Examples: Intel 80x86 (Pentium 4), IBM/Motorola PowerPC (Macintosh), MIPS, Intel IA64, ...

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MIPS Architecture

MIPS – semiconductor company that built one of the first commercial RISC architectures

MIPS is simple, elegant.Assembly Operands are registersGroups of 32 bits called a word in MIPS

The Text segment shows you:Address -- where this instruction is stored in memoryCode -- the machine code of the instructionBasic -- [not too helpful at this point]Source -- the original instruction you typed in

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List of Instructions

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Part 1: MIPS

Start the program with:

.textThis says that the following are program instructions (and not, e.g.,data) .

Let's do the following:

$t1 = 3 + 5 + 9First, let's put 3 in $t1:

addi $t1, $zero, 3

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Part 1: MIPS (cont…)

This says to take what is stored in register $zero, add 3 to it, and put the result in register $t1 .

$zero ALWAYS contains 0, so this puts 0 + 3 into register $t1

Now we want to add 5 to our running sum:

addi $t1, $t1, 5

And then we want to add 9:

addi $t1, $t1, 9

Save and Assemble the program (run it). You will see that $t1 contains 0x00000011

The 0x just means that the number following it is in hex.

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Performing the program

Pc : Special register keeping the address of next instruction . Read the code from memory by pc .

$at : assembler temporary as handle for save value .

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Questions

Question 1: What decimal number is 0x00000011?

Question 2: before the first instruction is executed (the program counter is the register labeled "pc")program counter = __________

Answer: 17

program counter = 0x00400000

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Cont..)) Questions

Question 3: after the first instruction is executed:program counter = $t1 =

Question 4: after the second instruction is executed:program counter =

$t1 = ____________

program counter = 0x00400004

$t1 = 0x00000003

program counter = 0x00400008

$t1 = 0x00000008

Cont..)) Questions

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Question 5: after the third instruction is executed:program counter = ___________ $t1 = _____________

Question 6: Complete this sentence:After each instruction, the PC is incremented so that it contains:1) A bit which is a 0 or 1.2) A byte which is 8 bits.3) A word which is 4 bytes.

program counter = 0x0040000C

$t1 = 0x00000011

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Cont..)) Questions

Hint : In a MIPS architecture, each byte has its own address (the byte is the "addressable unit"). 

Question 7: How big are instructions in MIPS ? Number of bits=

Number of bytes = Number of words =

324

1

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conclusion

This shows a good way to learn assembly language. Enter and assemble instructions; this will show you the machine code that is produced. Then, step through execution so you can see the effects of the individual instructions.

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exercise

f = (g + h) - (i + j)

to perform the calculation:

g= 5h= -20i= 13 j= 3

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H.W for absent

You are given the following two numbers in two’s complement representation.

Perform the binary addition and subtraction. Did signed overflow occur? determined whether or not overflow occurred.

0010110000101100

00101100

- 00101100