MCS-51 has 111 orders with 49 pieces of single-byte command type, 45 pieces of two-byte type commands, and 17 pieces of three-byte command type. This command can be grouped into four groups based on their function. MCS-51 has instructions with considerable amounts. Instructions can be incorporated into several groups. A list of the group can be seen in the table below:
1. Instructions Arithmetic
Arithmetic instructions include instructions that perform arithmetic processes, such as: addition, subtraction, multiplication, and division. Generally, this instruction using the accumulator as one of its operand
2. Instruction Logic
Instruction logic includes instructions that perform logic process on 8-bit registers. Generally, this instruction using the Accumulator or address (direct) as one of its operand
3. Instructions Boolean
Boolean instructions include instructions that involve only 1 bit saja.Instruksi using the carry flag or register 1 bit more as the operand
4. Branching Instruction (Branch)
Branching Instruction (Branch) include instructions that perform transfer processes to address. Instructions include: routine call (Call) and jump (Jump)
5. Data Transfer Instructions
Data Transfer Instructions include instructions to process the transfer or exchange of data involving registers 8 bit or 16 bit.