Motorola M68CPU32BUG Manuale Utente Scaricare il pdf (Pagina 9)

LAB 2

OBJECTIVES

In this experiment you will:

• Assemble, and download a given assembly program.

• Change the program’s functionality by directly altering the memory content.

• Learn the differences between the G (GO) debugger command and the T (TRACE)

command.

INTRODUCTION

The CPU can only execute a program which is in machine language form and already

stored in memory.

In Lab 1 we saw how a program is converted into machine language, stored in an S-

Record ﬁle and loaded into the main memory for execution.

A programmer these days will very rarely, if ever, need to work directly with machine lan-

uage. It is however important to have a good understanding of the process involved in

the machine code generation and execution by the CPU.

To convert assembly into machine code one needs the op-code for the instructions. The

instruction op-codes are well documented in the programmer’s reference documentation

of the CPU at hand. The 68000 programmer’s documentation is available in the addi-

tional lab documents. Appendix 4 contains a very small portion of that documentation for

some frequently used commands. The text book also contains the instructions along

with their op-codes.

Take a look at some of the instructions provided in Appendix 4 and identify the Instruction

Format and the tables that provide values for the Instruction Format ﬁelds.

In this experiment you will be downloading a program and then directly alter the memory

content to change the functionality of that program.

PRELAB

The following is to be performed prior to attending the scheduled lab session:

• Read Lab 2 in its entirety.

• Create the text ﬁle containing the source code for this lab in Appendix 1 in your com-

puter account.

• Familiarize yourself with Appendix 4 and the “hand-assembly” process. If necessary,

refer to your textbook. Hand assemble the changes indicated in the source code for this

lab.

Part 1: Assembly program compilation and download

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Motorola M68CPU32BUG Manuale Utente Pagina 9