Introduction
Communicationcontrolprocessor(CCP)
communicationcontrolprocessor
Foreachhostcomputer,hostcomputerandremoteAdevicethatcontrolsdatatransmissionandexchangebetweendataterminalsandbetweenremotedataterminals.Communicationcontrolprocessorswithdifferentfunctionscanconnectmultiplemaincomputers,communicationlines,andmanyuserterminalsintoacomputercommunicationnetwork,sothattheseuserscanusecomputersinthenetworkatthesametimeandshareresources.Thecommunicationcontrolprocessorcanusevariouscommunicationprotocolsandinterfaceconventionstoensurethecorrectandeffectivetransmission,transmission,receptionandprocessingofdataandinformation;makeiteasyforthehostcomputeroruserterminaltoaccessthecomputercommunicationnetworkflexibly,withouttheneedtomodifythenetworkforthispurposeDesign,computerdesignanduserterminaldesign;enablethemaincomputertoreleasenetworkcontroltasksandhavemoretimetoperformmainprocessingtasks.
Thecommunicationcontrolprocessorisusedtoconnectthecommunicationlineandthehostcomputer(host)orotherdatacommunicationequipment,andmanageallthecommunicationlinesconnectedtothedataterminalequipment(DTE).Eachindependentmulti-channelreceivingportcansimultaneouslyreceivedataofdifferentratesfromdifferentdatacommunicationequipment,andsendittothecommunicationlineaftercentralizedprocessingbyTDM,andsendittotheremotereceivingstation.Thecontrollercaninputcommandsfromtheconsoletoconnect,confirm,andcutoffthelinkcontrolofthelocalmachineortheremotereceivingstation.Thecommunicationcontrolprocessoriscomposedoftwoparts,ahardwarecircuitandasoftwarecontrolprogram,andthesoftwareplaysamoreimportantrole.
Basicfunctions
Typicalcommunicationcontrolprocessingfunctionsoperateaccordingtotherequirementsofcommunicationsoftware,separatingthecommunicationprocessingfunctionfromtheinformationprocessingofthehostcomputer,sothatthehostcomputerdoesnotneedtochangetheterminalType,linetype,transmissionmethodandnetworkprotocol,etc.Itsbasicfunctionsare:①Linecontrol:controltheonandoffofcommunicationlines,theinterfaceoflineterminationequipment(suchasmodems),andmonitorlinestatus.②Terminalcontrol:terminalselection,connectionandrelease,codingconversion,etc.③Organizemultiplecommunications:Transmitthedatafromeachcommunicationlinetothecomputercorrectlyatthesametime;distributethedatafromthecomputertothecorrespondingcommunicationline.④Combinationanddecompositionofcharacters:theserialcodefromthecommunicationlineisassembledandcombinedintoaparallelcodeandsenttothecomputer;theparallelcodefromthecomputerisdecomposedintoaserialcodeandsenttothecommunicationline.⑤Transmissioncontrol:theimplementationofcommunicationprocedures,thatis,thedatalinklayerprotocolofthenetworknodefunction.Thisregulationstipulatestherulesfordatatransmissionbetweentwoadjacentnodesonasinglelink,includingdataencoding,synchronizationmode,informationformat,operationsteps,etc.⑥Adjustmentoftransmissionspeedanddatabuffering:Thedatatransmissionrateonthecommunicationlineisgenerallylowerthantheinputandoutputtransmissionrateofthecomputer.Whentherearemultiplecommunicationlines,itisnecessarytosetabuffertoadjustthespeed.⑦Textandtelegramprocessing:automaticnumbering,combinationandcollection,analysisandediting,exchangeofrecords,errordiagnosis,etc.oftextandtelegrams.⑧Errorhandling:Useeffectiveerrordetectionandcorrectionmethodstofindandcorrecterrorsthatoccuronthecommunicationline,anduseerrorrecoveryprocedures,re-executionandothermeasurestocontrolothererrors.
Basicstructure
Centralcontrolpart
Itisthemainbodyofthecommunicationcontrolprocessor.Thecharacteristicsofthecommunicationcontrolprocessorare:
①Intheinstructionsystem,the"register-register"typeinstructionsarethemajority,themainmemoryaccessinstructionsarereduced,themultiplicationandfloating-pointoperationsinstructionshavebeendeleted,andsomespecialinstructionshavebeenadded.,Suchascycliccodeerrorcorrectioninstructions.
②Therearemultiplesetsofgeneralregisters,whichcanmakeuptohundredsofcommunicationlinesworkatthesametime.Inthecaseoffrequentinterruptions,thecostofsavingandrestoringthescenecanbereduced,therebyincreasingthetotalnumberofacceptablelinesandprocessingcapacity.
③Themainmemory(mainmemory)hasalargecapacity.Thecommunicationcontrolprocessorgenerallydoesnothaveauxiliarymemory,andthecommunicationsoftwareisstoredinthemainmemory.
④Itisequippedwithabufferdevice,whichcanbedividedintotwotypes:bytebufferandtext/messagebuffer.Theformerinterruptstheprocessormoretimesandtheprogramburdenislarger,butthedevicecapacityissmall,andismostlyusedingeneralcommunicationcontrollers;thelatterexchangesinformationwiththehostcomputerintheunitoftextandtelegrams,andeachcommunicationlinehasalargerBuffer,thenumberofinterruptsisless,andtheefficiencyishigher.
Linecontrolpart
Includestwoparts:lineinterfacepartandcommoncontrolpart.
①Lineinterfacecomponent:itsfunctionistoperformlevelconversionandinterfaceoperations.Therearemanytypesoflinesandterminals,anditisusuallynecessarytodesignavarietyoflineinterfacecomponents,allowinguserstoselectaccordingtotheirneedswhenthesystemisformed.Thelowestlayerinthenetworkfunctionofthecomputernetwork,thephysicallayer,mainlyreferstotheinterfacebetweenthelinecomponentsandthemodem.Itisimplementedbyhardware.Thephysicallayerprotocolisthestandardagreementforthisinterface.Theinterfacestandardspecifiesthename,function,electricalcharacteristics,andmechanicalcharacteristicsoftheinterfacelinesbetweendataterminalequipment.
②Commoncontrolcomponent:itsfunctionistocontrolthecombinationanddecompositionofcharactersandthescanningandsamplingoflineinterfacecomponents.Eachcircuithasacorrespondingstorageunitinthememory,butsharesasetofhardwarecontrolcircuits.Thelatterscanseachstorageunit;whenacertainunitisscanned,thecorrespondingcommunicationlineoccupiesthehardwarecontrolcircuitforcharactercombinationanddecomposition.Eachlinecanusethehardwarecontrolcircuitintime-sharingmode,andthestorageunitstoresthesceneofthelastoperationofthecorrespondingline
computerinterfacecontrolpart
andthecontrollerequippedwithinput-outputdeviceThecomputerinterfaceisthesame.
ClassificationThecommunicationcontrolprocessorisdividedintofivetypesaccordingtothefunctionofthecomputernetworknode:communicationinterface,communicationcontroller,front-endprocessor,terminalprocessorandnodeprocessor.
CommunicationinterfaceItonlyhasthelinecontrolpartinthebasicstructure,whichcompletesthelinecontrolandmulti-channelcontrolinthebasicfunction.Itscharacteristicisthatitisbit-basedSend,receiveandbuffercharactersortextmessages.
CommunicationControllerIthasthreepartsofthebasicstructure,andhasotherbasicfunctionsbesidesthetransmissionandprocessingfunctions.Itischaracterizedbysendingandreceiving,bufferingandprocessingtextmessagesaccordingtocharactersor"frames"or"packets".
Front-endprocessorIthasstrongtransmissioncontrolandtextprocessingcapabilities.Itscharacteristicistosendandreceive,bufferandprocessinunitsofmessagesandtelegrams.Itiscomposedofsmallcomputers.Whenthecommunicationcontrolmodeischanged,itisnotnecessarytochangethewiringbetweenthemachinesbutonlyneedtomodifythehardwareandsoftwareslightly,soithasgreaterflexibilityandeconomy.
TerminalProcessorWhentheuserterminaldoesnothavealocalhostcomputeravailableorthelocalhostcomputerdoesnothaveatime-sharingsystem,itallowstheuserterminaltoenterThecomputernetworkenjoyscomputerresources.Ithasastrongterminalcontrolfunction.
NodeprocessorItcanstrengthenthetransmissioncontrolfunctioninthebasicfunction,connectthecommunicationlinesinthecomputernetworktoeachother,andrealizetheconversionofdataformatandcommunicationprocedures.Itscharacteristicisthatitisnotdirectlyconnectedtothehostcomputeroruserterminal.