Program branching and bit manipulation instructions of 8051 microcontroller

 

Program branching instructions of 8051 microcontroller

Program branching instructions are used to access the modules/subroutines or small programs that are written apart from main program to overcome the redundancy in the codes.

Absolute call (ACALL) = 11 bit add

Long call (LCALL)       = 16 bit add

 

ACALL ADD11;

This instruction is absolute subroutine call instruction which specifies 11 bit address and calls subroutines written within 2k memory

 

LCALL ADD16;

This instruction is long subroutine call instruction which specifies 16 bit address and calls subroutines written within 64k memory

 

RET ;

Return from subroutine

 

RETI;

Return from interrupt

 

AJMP ADD11   ;

This instruction is absolute subroutine JUMP instruction which specifies 11 bit address and JUMPS subroutines written within 2k memory

 

 

LJMP ADD16   ;

This instruction is long subroutine JUMP instruction which specifies 16 bit address and JUMPS subroutines written within 64k memory

 

SJMP REL;

(ALTERNATIVE INSTRUCTION FOR END) This is short jump instruction which specifies 8-bit add

 

JZ REL;

Jump to relative address when accumulator is zero

 

JNZ REL;

Jump to relative address when accumulator is non zero

 

CJNE A,DIRECT,REL       ;

Compare direct bit with accumulator and jump to relative address when not equal (compare and jump if not equal)

 

CJNE A,#12H,REL;

Compare 8-bit data with accumulator and jump to relative address when not equal (compare and jump if not equal)

 

DJNZ R0,REL;

Decrement the contents of R0 and jump to relative add if not zero

 

NOP;

No operation

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Bit manipulation instructions

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Bit manipulation instructions

CLR C                 ; clears (0) carry flag

CLR BIT             ; clears bit

SETB C               ; sets (1) carry flag

SETB BIT           ; sets (1) bit

CPL C                 ; complements/inverts carry flag

CPL BIT             ; complements bit

ANL C,BIT         ; AND carry flag and bit      

ANL C,/BIT        ; AND carry flag and inverse of bit

ORL C, BIT        ; OR carry flag and bit

ORL C,/BIT        ; OR carry flag and inverse of bit

MOV C, BIT      ; move direct bit into carry flag

JC REL_ADD    ; Jump to relative address when carry is generated

JNC REL_ADD ; Jump to relative address when there is no carry

JB REL_ADD    ; Jump to relative address when bit is set

JNB REL_ADD ; Jump to relative address when bit is not set