Sunday, February 28, 2016

8051 External Addressing Mode

External Addressing Mode

  • In many applications the size of program code does not leave any room to share the 64K-byte code space with data. The 8051 has another 64K bytes of memory space set aside exclusively for data storage. This data memory space is referred to as external memory and it is accessed only by the MOVX instruction.
  • External data memory (XRAM) is a third address space, also starting at address 0, and allowing 16 bits of address space
  • It can also be on- or off-chip
  • It must be accessed using the MOVX (Move external) instruction
  • Example:
  • MOVX A, R0
    MOVX A, R1
    MOVX @R0, A
    MOVX @R1, A

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

List of topics: 8051

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