Addressing modes of 8051 microcontroller

1. ADDRESSING MODES OF 8051
by
-SHARIQUE MULLA
13/3/2015 SHARIQUE MULLA

2. WHAT IS AN ADDRESSING MODE?
• An Addressing mode is a way to address an
operand.
• Operand means the data we are operating upon
(in most cases source data).
• It can be a direct address of memory, it can be any
numerical data, etc.
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3. ADDRESSING MODES
1. Immediate addressing mode
2. Direct addressing mode
3. Register direct addressing mode
4. Register indirect addressing mode
5. Indexed addressing mode
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4. 1) IMMEDIATE ADDRESSING MODE
• This type of addressing mode is named as
“immediate addressing”, because it transfers
an 8-bit data immediately to the accumulator
(destination register).
• This instruction has an 8-bit immediate data
at the operand.
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5. • Example- MOV A,#6AH
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6. 2) DIRECT ADDRESSING MODE
• This is an another way of addressing an
operand.
• In this type of addressing mode, the address
of the data (source data) is given as operand
instead of immediate data .
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7. • Example- MOV A,04H
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8. 3) REGISTER DIRECT ADDRESSING
MODE
• In this type of addressing mode, we use the
register name directly as source operand.
• In 8051,there are 4 register banks, containing 8
registers (R0-R7) each.
• Hence, the selection of a register bank is done by a
special function register (SFR) called Processor
Status Word (PSW).
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9. • Example- MOV A,R4
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10. 4) REGISTER INDIRECT ADDRESSING
MODE
• In this type of addressing mode, the address of the
data (source data) is given in the register operand.
• Here also, the register bank is required to be
selected by PSW (Processor Status Word).
• Here, the selected register is first loaded with a
value which acts as the address of the data.
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11. • Example- MOV A,@R0
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12. 5) INDEXED ADDRESSING MODE
• In this type of addressing, DPTR (Data Pointer) or
PC (Program Counter), i.e. 16-bit registers, are
used in the instruction.
• Here, the content of DPTR or PC is added to the
current content of accumulator.
• The result acts as the address of the source data.
• After execution the source data is stored in
accumulator.
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13. • Example- MOV A,@A+DPTR
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14. PROCESSOR STATUS WORD (PSW)
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15. THANK YOU
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