CH6 Program control instructions(程序控制命令).ppt

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1、Chapter6Programcontrolinstructions6-1theJUMPgroup6-2ControllingtheFlowofanassemblylanguageprogram6-3procedures6-4introductiontointerrupts6-5machinecontrolandmiscellaneousinstructions6-1TheJUMPgroupUnconditionaljump(JMP)Shortjump1000:0100JMP01058-bitdisplacementDistanceforjump:-128~127

2、Nearjump1000:0100JMPNEAR0105jumpwithincurrentsegment16-bit/32-bitdisplacementfor8086/80386Distanceforjump:±32K/±2GFarjump1000:0100JMPFAR2000:0000Jumptoanylocationsegment:offsetaddresscontainedintheinstructions6-1TheJUMPgroupUnconditionaljumpJumpwithregisteroperandsJMPAXIndirectjumpJMP

3、[SI]JMP[BX+100H]6-1TheJUMPgroupConditionaljumpsandconditionalsetsAboveorbelowForcomparingunsignednumbersCarryistestedGreaterorlessForcomparingsignednumbersSignflagsistestedConditionaljumpAssemblylanguageConditionaltestedoperationJAZ=0andC=0JmpifaboveJAEC=0JumpifaboveoreuqalJBC=1Jumpif

4、belowJBEC=1orZ=1JumpifbeloworequalJCC=1JumpifcarrysetJEorLZZ=1JumpifequalorjumpifzeroJGZ=0andS=0JumpifgreaterthanJGES=0JumpifgreaterthanorequalJLS<>0JumpiflessthanJLES<>orZ=1JumpiflessthanorequalJNCC=0JumpifnocarryJNEorJNZZ=0JumpifnotequalorjumpifnotzeroJNOO=0JumpifnooverflowJNSS=0Jum

5、pifnosignJNPorJPOP=0JumpifnoparityorjumpifparityoddJOO=1JumpifoverflowJPorJPEP=1JumpifparitysetorjumpifparityevenJSS=1JumpissignissetJCXZCX=0JumpifCXiszeroJECXZECX=0JumpifECXiszeroExampleforconditionaljumpMOVAX,1234HMOVBX,1000HCMPAX,BXJGIF_GREATERMOVCX,1JMPNEXT_1IF_GREATER:MOVCX,0NEXT

6、_1:RETAX=1234HBX=1000HIfAX>BXCX=0ElseCX=16-1TheJUMPgroupLoopCXisdecrementedJumpstotheaddressindicatedifCX<>0Example:for(CX=10;CX>=0;CX--){}MOVCX,10;Label1:NOPLOOPLabel1NOPisexecutedby10times.LoopLoopLoopwLoopdConditionalloopLOOPEloopwhileequalLOOPNEloopwhilenotequal6-3ProceduresExampl

7、e6-16SUMSPROCNEARADDAX,BXADDAX,CXADDAX,DXRETSUMSENDPSUMS1PROCFARADDAX,BXADDAX,CXADDAX,DXRETSUMS1ENDP6-3ProceduresCallinstructionNearcallOperationPushtheoffsetfornextinstructionintothestackAddthedisplacementtoIPCallprocedureswithinthesegment(±32K)FarcallOperationPushthesegment&offsetad

8、dress