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.