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Input/Output Instructions

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IN 8-bit addr:
  • This instruction is used to copy the data from the port into the accumulator.
  • The address of the port is given in the instruction.
 OPERATION: A = (8-bit addr)
  • No flags are affected.
  • It is a two byte instruction.
  • Direct addressing mode is used.
Example:
If port address = 20H, (20H) = 08H, then
IN 20H ; This instruction will copy the data stored at port address 20H i.e. 08H into the accumulator.

OUT 8-bit addr:
  • This instruction is used to copy the contents of the accumulator to the output port.
  • The address of the port is given in the instruction.
OPERATION: (8-bit addr) = A
  • No flags are affected.
  • It is a two byte instruction.
  • Direct addressing mode is used.
Example:
If A = 08H, then
OUT 20H ; This instruction will copy the contents of the accumulator i.e. 08H to the port whose address is 20H.
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