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embeddedmicrocontroller8051

Why is the value of SP register 07h when 8051 is powered up?

When the 8051 is powered up, the Stack pointer register contains value 07h not 00h?

Solution

  • Because of Bank 0 is the default register bank used by 8051. This bank 0 uses registers 0 - 7.

    If the SP starts from 0 registers R0 - 7 would overwrite the SP and cause undefined behavior, at least.

    Usually the SP is set to the desired location with startup code