Intel MCS 51 User Manual

i~.
MCS@-5fPROGRAMMER’SGUIDE AND INSTRUCTION SET
JB bityrei
Function:
Description:
Bytes:
Cycierx
Encoding:
Operstion:
JBC bitrei
Jumpif Bit set
If the indicatedbit is a one,jump to the addreasindicat@ otherwiseproceedwith the next
instruction.Thebranch destinationis computedbyaddingthe signedreistive-displscem
ent in
the third instruction byte to the PC, after incrementingthe PC to the fnt byte of the next
instruction.The
bit tested k nor modified. No tlags are affected.
The data
present at inputport 1is 11OO1O1OB.The Accumulatorhoids56(O1O1O11OB).The
instructionsequence,
JB P1.2,LABEL1
JB ACC.2,LABEL2
willcauseprogram executionto branch to the instructionat label LABEL2.
3
2
0010
1004 EEzEEl EizEl
JB
(PC)+ (PC)+
3
IF (bit) = 1
THEN
(PC) +- (PC) + rel
Function: lump if Bit is setandClearbit
Description:
If the indicatedbit is one,branch to the addressindicated;otherwiseproceedwith the next
instruction.17re
bit wili not be cleared ~~itis already a zero. The branchdestinationiscomput-
ed by adding the signedrelative-displacementin the third instructionbyte to the PC, after
incrementingthe PC to the tlrst byte of the nextinstruction.No flagsare affected.
Note:When this instructionis used to test an output pin, the valueusedas the originaldata
willbe read from the output data latch, notthe inputpin.
Exempie:
The
Accumulatorholds56H(01010110B).Theinstructionsequence,
JBC ACC.3,LABELI
3BC ACC.2,LABEL2
willcauseprogram executionto continueat the instructionidentifiedby the label LABEL2,
withthe Accumulatormodifiedto 52H (OIO1OO1OB).
2-46

Intel MCS 51 Specifications

General

Brand	Intel
Model	MCS 51
Category	Microcontrollers
Language	English