Question
Download Solution PDFHow does the 8051 microcontroller access external memory?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
The 8051 microcontroller accesses external memory primarily through indirect addressing using the Data Pointer (DPTR).
Here's why:
-
DPTR (Data Pointer): The DPTR is a 16-bit register in the 8051 that holds the 16-bit address of the external memory location to be accessed.
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MOVX Instruction: The 8051 uses special instructions like
MOVX(Move External) to read from or write to external data memory. For example,MOVX A, @DPTRmoves data from the external memory location pointed to by DPTR into the accumulator. -
Indirect Addressing: This method is called indirect addressing because the instruction doesn't directly specify the memory address but rather uses the content of a register (DPTR) as the address.
While the 8051 also has direct, immediate, and register addressing modes, these are primarily for accessing internal memory (RAM, SFRs) or for immediate data operations, not for accessing external memory.
Therefore, the correct option is: By using indirect addressing through DPTR
Last updated on Jul 2, 2025
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