Sunday, February 28, 2016

8051 Indirect Addressing Mode

Indirect Addressing Mode

8051 Direct and Indirect Addressing Mode

  • This mode uses pointer to hold the effective address of the operand
  • Only registers R0, R1 and DPTR can be used as pointer register
  • R0 and R1 can hold 8-bit address
  • DPTR can hold 16-bit address
  • DPTR is useful in accessing operands in external memory
  • Operand address is determined during run-time
  • Make data accessing dynamic
  • Indirect addressing is represented by a @ before R0 or R1 or DPTR
  • Indirect addressing always refers to 128 bytes (00H – 7FH) of Internal RAM
  • Example:
  • MOV @R0, A
    The above instruction store the content of accumulator in memory location pointed by R0
    MOV A, @DPTR
    The above instruction transfer the content from memory location pointed by DPTR in to accumulator

8051 Indirect Addressing Mode Example

Related topics:
8051 Addressing Modes   |   8051 Register Addressing Mode   |   8051 Direct Addressing Mode   |   8051 Immediate Addressing Mode   |   8051 Relative Addressing Mode   |   8051 Absolute Addressing Mode   |   8051 Long Addressing Mode   |   8051 Indexed Addressing Mode   |   8051 External Addressing Mode

List of topics: 8051

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