08-11-2012, 03:34 PM
DATA ADDRESSING MODES
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Introduction
• Efficient software development for the
microprocessor requires a complete familiarity
with the addressing modes employed by each
instruction.
• This chapter explains the operation of the
stack memory so that the PUSH and POP
instructions and other stack operations will
be understood.
Chapter Objectives
• Explain the operation of each data-addressing
mode.
• Use the data-addressing modes to form
assembly language statements.
• Explain the operation of each program
memory-addressing mode.
• Use the program memory-addressing modes
to form assembly and machine language
statements.
• Select the appropriate addressing mode to
accomplish a given task.
• Detail the difference between addressing
memory data using real mode and pro-tected
mode operation.
• Describe sequence of events that place data
onto the stack or remove data from the stack.
• Explain how a data structure is placed in
memory and used with software.
3–1 DATA ADDRESSING MODES
• MOV instruction is a common and flexible
instruction.
– provides a basis for explanation of dataaddressing
modes
• Figure 3–1 illustrates the MOV instruction and
defines the direction of data flow.
• Source is to the right and destination the left,
next to the opcode MOV.
– an opcode, or operation code, tells the
microprocessor which operation to perform
Immediate Addressing
• Term immediate implies that data immediately
follow the hexadecimal opcode in the memory.
– immediate data are constant data
– data transferred from a register or memory
location are variable data
• Immediate addressing operates upon a byte or
word of data.
• Figure 3–4 shows the operation of a MOV
EAX,13456H instruction.
• In symbolic assembly language, the symbol #
precedes immediate data in some
assemblers.
– MOV AX,#3456H instruction is an example
• Most assemblers do not use the # symbol,
but represent immediate data as in the MOV
AX,3456H instruction.
– an older assembler used with some Hewlett-
Packard logic development does, as may others
– in this text, the # is not used for immediate data