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Teachics

Arithmetic Instructions in 8085

Arithmetic instructions perform various arithmetic operations such as addition, subtraction, increment, and decrement.

Commonly used arithmetic operations are:

  • Add
  • Subtract
  • Increment
  • Decrement

The complete list of arithmetic instructions in 8085 is described in the following table.

Mnemonic Description Example
ADD R 1-byte instruction
Adds the contents of register R to the contents of the accumulator.
ADD B
ADI 8-bit 2-byte instruction
Adds the second byte to the contents of the accumulator.
ADI 57H
ADD M Adds the content of memory to A; the address of memory is in HL register. ADD M
SUB R 1-byte instruction
Subtracts the contents of register R from the contents of the accumulator.
SUB B
SUI 8-bit 2-byte instruction
Subtract the second byte from the contents of the accumulator.
SUI 34H
SUB M Subtracts the content of memory from A; the address of memory is in HL register. SUB M
INR R 1-byte instruction
Increases the contents of register R by 1
Caution: All flags except the CY are affected.
INR D
INR M Increments the content of memory the address of which is in HL register. INR M
DCR R 1-byte instruction
Decreases the contents of register R by 1
Caution: All flags except the CY are affected
DCR B
DCR M Decrements the content of memory the address of which is in HL register. DCR M
INX Rp Increments the content of the register pair. INX H
DCX Rp Decrements the content of the register pair. DCX B

All instructions except INR and DCR,

  • Assume that the accumulator is one of the operands.
  • Modifies all the flags according to the data conditions of the result.
  • Place the result in the accumulator.
  • Do not affect the contents of the operand register.

The INR and DCR instructions affect the contents of the specified register and all flags except the CY flag.

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