8051 Assembly Language Programming

Assembly and  Running 8051 Micro-Controller

• Editor- It is a source file where the programmer writes 8051 assembly language program.
• This file is saved as "filename.asm" (asm = assembly)
• Assembler - It converts assembly language into machine language 
• It generates two files-
• "filename.lst" -list file which contains sources of error and comments by programmers.(lst = list)
• "filename.obj" - file containing machine language code. (obj = object)
• Linker program - It relocates and links all the related files to create one absolute file
• It create one file named "filename.abs" (abs = absolute) 
• OH program - It converts the object code to hexadecimal code which can be burnt into target machine.
• It generate file called "filename.hex" (hex = hexadecimal)

8051 Assembly Directives

They are the instruction directly gives to assembler

• ORG - Origin, It denotes the starting address of the program
• ORG 2000H
• END - End, It denotes the end of program. 
• END
• EQU - Equal, associates a number with variable which can later be used in the program.
• COUNT EQU 25
• MOV R3 , #COUNT

Note - Without # it is a memory location. With # it is data.

Instructions

• ACALL - Absolute Call
• ADD, ADDC - Add Accumulator (With Carry)
• AJMP - Absolute Jump
• ANL - Bitwise AND
• CJNE - Compare and Jump if Not Equal
• CLR - Clear Registerr
• CPL - Complement Register
• DA - Decimal Adjust
• DEC - Decrement Register
• DIV - Divide Accumulator by B
• DJNZ - Decrement Register and Jump if Not Zero
• INC - Increment Register
• JB - Jump if Bit Set
• JBC - Jump if Bit Set and Clear Bit
• JC - Jump if Carry Set
• JMP - Jump to Address
• JNB - Jump if Bit Not Set
• JNC - Jump if Carry Not Set
• JNZ - Jump if Accumulator Not Zero
• JZ - Jump if Accumulator Zero
• LCALL - Long Call
• LJMP - Long Jump
• MOV - Move Memory
• MOVC - Move Code Memory
• MOVX - Move Extended Memory
• MUL - Multiply Accumulator by B
• NOP - No Operation
• ORL - Bitwise OR
• POP - Pop Value From Stack
• PUSH - Push Value Onto Stack
• RET - Return From Subroutine
• RETI - Return From Interrupt
• RL - Rotate Accumulator Left
• RLC - Rotate Accumulator Left Through Carry
• RR - Rotate Accumulator Right
• RRC - Rotate Accumulator Right Through Carry
• SETB - Set Bit
• SJMP - Short Jump
• SUBB - Subtract From Accumulator With Borrow
• SWAP - Swap Accumulator Nibbles
• XCH - Exchange Bytes
• XCHD - Exchange Digits
• XRL - Bitwise Exclusive OR