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Stack Operations Instructions (Part-II) - SPHL and XTHL

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SPHL:
  • This instruction copies the contents of HL register pair to the stack pointer (SP).
  • It means that the stack pointer will now point to the memory location whose address was given in the HL register pair.
  • No flags are affected.
  • It is a one byte instruction.
  • Register addressing mode is used.
Example:
If HL = 2030H, then
SPHL ; This instruction will copy 2030H into SP. So SP will point to the memory location 2030H.

XTHL:
  • This instruction exchanges the contents of the memory location pointed by stack pointer with the contents of the L register and the contents of the next memory location with the contents of H register.
  • This instruction does not alter the contents of the stack pointer.
  • No flags are affected.
  • It is a one byte instruction.
  • Register Indirect addressing mode is used.
Example:
If HL = 5601H, SP = 2000H, (2000H) = 30H and (2001H) = 20H, then
XTHL ; This instruction will exchange the contents of the memory location 2000H i.e. 30H with the contents of L register i.e. 01H and the contents of memory location 2001H i.e. 20H with the contents of H register i.e. 56H.

Before execution:
After execution:
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