ABB DCS 系统 培训课程 系列讲座 Code sorting

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1、CourseT530Chapter18Codesorting18.1GeneralInformation18.1.1DescriptionThischapterdescribesthedifferentmethodsofcodesortingandhowtohandleloops.18.1.2ObjectivesOncompletionofthischapteryouwillbeableto:·Describethedifferencesbetweendifferentmethodsofcodesorting·De

2、scribetheadvantagesofeachmethod·Analyzeandsolveloopsintheprogramcode.18.1.3ReferenceDocumentationUsetheonlinehelp:Contentstab,ControlModuleDiagramEditor>WorkingwithControlModules18.23BSE022868/A2000/12/516:27:0018-7CourseT530Lesson1-Codesorting18.1.1Descriptio

3、nThischapterdescribesthedifferentmethodsofcodesortingandhowtohandleloops.18.1.2ObjectivesOncompletionofthislessonyouwillbeableto:·Describethedifferencesbetweendifferentmethodsofcodesorting·Describetheadvantagesofeachmethod·Analyzeandsolveloopsintheprogramcode.

4、18.1.3AccordingtoIEC61131-3Theexecutionorderoffunctionblocksfollowstheprogramflowasimplementedbytheprogrammer.18.1.4ControlModuleCodeSorting-introductionForControlModules,thecompileranalyzeseachcodeblock(ST,IL,FBD,andLD-SFCistreatedsomewhatdifferently,seeremar

5、kbelow)separatelywithrespecttowhichvariablesthatarereadandwritten,respectively,byeachblock.Thecompilerthendeterminestheoptimalexecutionorder.Acodeblockthatassignsavaluetoavariablehastobeexecutedbeforetheblockthatreadsthevariablevalue(comparefigurebelowinwhicht

6、hecodeblockincontrolmodule1mustbeexecutedbeforethecodeblockincontrolmodule2).Thetechniqueiscalledcodesortingandmeansthattheoptimalexecutionorderwillbebasedondataflowinsteadofprogramflow(asisthecaseforfunctionblocks).Codesortingguaranteesthatthecodewillbeexecut

7、edincorrectorder.Codesortingsuppressestime-delaysandresultsinthatanewcontrolmoduleautomaticallybecomescorrectlyplacedintheprocess.3BSE022868/A2000/12/516:27:0018-7CourseT530ForanyfromcontrolmodulescalledFunctionBlocks,itisonlytheparameterinterface(In,Out,orIn_

8、out)thataffectsthecode-blocksorting.Thatis,noanalysisismadeonhowtheFunctionBlocksactuallyusetheparameters.Inaddition,FunctionBlockreferencestoexternalvariablesdonotaffecttheexecuti