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8051 Instruction Set. In this lecture we will look at the various addressing modes and the instructions. The 8051 Architecture course would be helpful in understanding some of the concepts presented in this course. An instruction is made up of an operation code (op-code) followed by operand(s).
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Opcodes. Home » Opcodes. The following table lists the 8051 instructions by HEX code. Hex. Code. Bytes. Mnemonic. Operands. 00.
8051 Microcontroller Instruction Set. Atmel 8051 Microcontrollers Hardware Manual. 1-6. 0509C–8051–07/06. 1.1 Instruction Definitions. ACALL addr11. Function: Absolute Call. Description: ACALL unconditionally calls a subroutine located at the indicated address.
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Description: JBC will branch to the address indicated by reladdr if the bit indicated by bit addr is set. Before branching to reladdr the instruction will clear the indicated bit. If the bit is not set program execution continues with the instruction following the JBC instruction. See Also: JB, JNB.
- A Brief Look at 8051 Microcontroller Instructions and Groups
- 8051 Addressing Modes
- Types of Instructions in 8051 Microcontroller Instruction Set
- Data Transfer Instructions
- Arithmetic Instructions
- Logical Instructions
- Boolean Or Bit Manipulation Instructions
- Program Branching Instructions
Before going into the details of the 8051 Microcontroller Instruction Set, Types of Instructions and the Addressing Mode, let us take a brief look at the instructions and the instruction groups of the 8051 Microcontroller Instruction Set (the MCS-51 Instruction Set). The following table shows the 8051 Instruction Groups and Instructions in each gro...
What is an Addressing Mode?
An Addressing Mode is a way to locate a target Data, which is also called as Operand. The 8051 Family of Microcontrollers allows five types of Addressing Modes for addressing the Operands. They are: 1. Immediate Addressing 2. Register Addressing 3. Direct Addressing 4. Register – Indirect Addressing 5. Indexed Addressing
Immediate Addressing
In Immediate Addressing mode, the operand, which follows the Opcode, is a constant data of either 8 or 16 bits. The name Immediate Addressing came from the fact that the constant data to be stored in the memory immediately follows the Opcode. The constant value to be stored is specified in the instruction itself rather than taking from a register. The destination register to which the constant data must be copied should be the same size as the operand mentioned in the instruction. Example: MO...
Register Addressing
In the 8051 Microcontroller Memory Organization Tutorial, we have seen the organization of RAM and four banks of Working Registers with eight Registers in each bank. In Register Addressing mode, one of the eight registers (R0 – R7) is specified as Operand in the Instruction. It is important to select the appropriate Bank with the help of PSW Register. Let us see a example of Register Addressing assuming that Bank0 is selected. Example: MOV A, R5 Here, the 8-bit content of the Register R5 of B...
Before seeing the types of instructions, let us see the structure of the 8051 Microcontroller Instruction. An 8051 Instruction consists of an Opcode (short of Operation – Code) followed by Operand(s) of size Zero Byte, One Byte or Two Bytes. The Op-Code part of the instruction contains the Mnemonic, which specifies the type of operation to be perfo...
The Data Transfer Instructions are associated with transfer of data between registers or external program memory or external data memory. The Mnemonics associated with Data Transfer are given below. 1. MOV 2. MOVC 3. MOVX 4. PUSH 5. POP 6. XCH 7. XCHD The following table lists out all the possible data transfer instructions along with other details...
Using Arithmetic Instructions, you can perform addition, subtraction, multiplication and division. The arithmetic instructions also include increment by one, decrement by one and a special instruction called Decimal Adjust Accumulator. The Mnemonics associated with the Arithmetic Instructions of the 8051 Microcontroller Instruction Set are: 1. ADD ...
The next group of instructions are the Logical Instructions, which perform logical operations like AND, OR, XOR, NOT, Rotate, Clear and Swap. Logical Instruction are performed on Bytes of data on a bit-by-bit basis. Mnemonics associated with Logical Instructions are as follows: 1. ANL 2. ORL 3. XRL 4. CLR 5. CPL 6. RL 7. RLC 8. RR 9. RRC 10. SWAP T...
As the name suggests, Boolean or Bit Manipulation Instructions deal with bit variables. We know that there is a special bit-addressable area in the RAM and some of the Special Function Registers (SFRs) are also bit addressable. The Mnemonics corresponding to the Boolean or Bit Manipulation instructions are: 1. CLR 2. SETB 3. MOV 4. JC 5. JNC 6. JB ...
The last group of instructions in the 8051 Microcontroller Instruction Set are the Program Branching Instructions. These instructions control the flow of program logic. The mnemonics of the Program Branching Instructions are as follows. 1. LJMP 2. AJMP 3. SJMP 4. JZ 5. JNZ 6. CJNE 7. DJNZ 8. NOP 9. LCALL 10. ACALL 11. RET 12. RETI 13. JMP All these...
A51: Defining New Instructions with Macros. The following pages describe the 8051 instruction set. Instructions are listed in alphabetical order and each is divided into several sections: Description Describes the instruction's effect and describes any arguments. See Also Names related instructions.
Rev. 4316E–8051–01/07 Section 1 The 8051 Instruction Set The 8051 instruction set is optimized for 8-bit control applications. It provides a variety of fast addressing modes for accessing the internal RAM to facilitate byte operations on small data structures. The instruction set provides extensive support for one-bit vari-
