8051 Jump if Bit Set

Jump if Bit set

JB bit address, relative address
If the indicated bit is a one, JB jump to the address indicated; otherwise, it proceeds with the next instruction. The branch destination is computed by adding the signed relative-displacement in the third instruction byte to the PC, after incrementing the PC to the first byte of the next instruction. The bit tested is not modified. No flags are affected.

Encoding: 0 0 1 0 0 0 0 0 bit address rel. address

The data present at input port 1 is 11001010B. The Accumulator holds 56 (01010110B). The following instruction sequence,

JB P1.2,LABEL1

JB ACC. 2,LABEL2

causes program execution to branch to the instruction at label LABEL2.

Example:

	ORG 0H
MAIN :
	MOV A, #0	; Clear accumulator
	MOV A, #10H
	ADD A, P0
	JB P0.1, LABEL1
	JB ACC.2, LABEL2
	ADD A, #5H
LABEL1 :	SUBB A, #4H
	AJMP MAIN
LABEL2 :	SUBB A, #2H
	AJMP MAIN
	END

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Related topics:
8051 Unconditional and Conditional Jump   |   8051 Long Jump   |   8051 Absolute Jump   |   8051 Short Jump   |   8051 Indirect Jump   |   8051 Jump if Accumulator Zero   |   8051 Jump if Accumulator Not Zero   |   8051 Compare and Jump if Not Equal   |   8051 Decrement and Jump if Not Zero   |   8051 Jump if Carry is Set   |   8051 Jump if Carry is Not Set   |   8051 Jump if Bit Not Set   |   8051 Jump if Bit is Set and Clear Bit

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List of topics: 8051

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