Lab SessionIV CSIT120 Fall 2000

1
Lab Session-IV CSIT-120 Fall 2000

• Precedence Rules
• Machine Language Programming
• The Micro Machine
• The Micro Simulator
• The Micro Translator (Thanks to Genti)
• Experiment 4.1 and Lab Exercise 4-B
• Experiment 4.2
• Lab 4 Continued

2
Mixing Arithmetic Operations

• When we try to perform several arithmetic
  operations in one expression, the expression
  becomes quite complex
• For example, consider the following
• Q (ABC)(AB/C)
• Q ((AB)C)((AB)/C)???
• Q (A(BC))(A(B/C))???

3
Precedence Rules

• In order to resolve complex expressions without
  any ambiguity, a set of precedence rules is
  defined
• ( )Parenthesis have top priority
• In arithmetic operations, and / take precedence
  over and -
• has lowest priority

4
Machine Language Programming

• All programs written in C, Java or any other
  user-level language are translated to the machine
  language after compilation
• Look at an example that shows how a C program
  line will be converted to the machine language of
  Micro, an example machine

5
The Compilation of Programs
6
Machine Language Programs

• A compiled and linked program is a series of
  machine language instructions and data
• Each processor has its own set of machine
  language instructions
• Can programs compiled for Pentium II run on Alpha
  workstation?

7
The Micro Machine

• The Micro Machine has
• 256 Memory cells, each cell can hold 1 byte
• Memory addresses range 00-FF (two digits)
• 16 General Purpose Registers
• Register addresses range 0-F (one digit)
• Program Counter and Instruction Register
• 12 Machine Language Instructions (1-C)

8
The Micro Simulator

• The Micro Simulator is a C Program
• Download this program by visiting The Micro
  link in the labs webpage of the course
• Click on micro to download or cut paste this
  program and save as a C file
• Double click on this file to run Visual C
• Compile and run the program

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The Micro Simulator

• The full screen display shows the contents of the
  memory from cell 00 to cell FF
• It also shows contents of registers R0 through
  R15
• PC and IR contents are visible too
• The machine has several single-letter commands
• (4-A) Experiment 4.1 (PC incr?)

10
Gentis Translator

• It is obvious that writing hex code is cryptic
  and prone to errors.
• If anything goes wrong, it is difficult to trace
  the errors (or debug the code)
• To make it human-friendly, Our TA last semester
  Mr. Genti developed a translator for the assembly
  language of micro

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Gentis Translator

• This translator assumes the program is written
  using some suggested mnemonics
• Following is a list of instructions and their
  corresponding hex code and mnemonics

12
Gentis Translator
13
Strategy for Programming Micro

• Develop your program using this list in a text
  file using wordpad or notepad
• Run Gentis translator by using the link given in
  the course web pages
• Program asks for input file name and output file
  name
• It will leave the hex code in a text file
• Keep that file in view when you load the program
  into micro simulator

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The Power to Simulate

• The Micro Simulator can run programs designed by
  you too
• Lab Exercise 4-B
• Design a program that adds values 1 through 5
  together and leaves the result in register R9.
  These values should be loaded into the memory by
  hand.
• (4-C) Experiment 4.2

15
Lab-4 Continued

• The Micro Machine and its Simulator
• The JUMP instruction and its usage
• Experiment 4.4

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Micro and its Simulator

• What is the memory size in Micro?
• How many instructions are there?
• How can we start executing a program in Micro?
• What is the difference between S and G commands?
• What does Gentis Translator do?

17
JUMP Instruction

• JUMP instruction is provided to facilitate the
  implementation of loops and branches
• Its format is B RXY (JUMP RXY)
• It means jump to location XY if RR0
• Unconditional jump if R0 compared to itself
• Experiment 4.4