These instructions affect the operation of the microprocessor. Halt and No operation are the two program control or machine control instructions.
| Opcode | Description |
|---|---|
| HLT | Halt 1-byte instruction. The processor stops executing and enters waiting state. The address bus and databus are placed in high impedance state. Register contents are not affected. |
| NOP | No Operation 1-byte instruction. No operation is performed. Generally used to increase processing time or substitute in place of an instruction. |