Hardware system

Singlebusstructure

Thatis,agroupofsystembusesisusedtoconnectthevariouspartsofthecomputersystem,andthevariouspartscanexchangeinformationthroughthebus.TheadvantageofthisstructureisthatitiseasytoexpandnewI/Odevices,andtheregistersofvariousI/Odevicesandthestorageunitsofthemainmemorycanbeaddresseduniformly,makingitmoreconvenientandflexiblefortheCPUtoaccessI/Odevices;itsdisadvantageisAtthesametime,onlyapairofsettingshangingonthebuscantransmitinformationtoeachother,thatis,time-sharinguseofthebus,whichlimitsthethroughputofinformationtransmission.Thisstructureisgenerallyusedinmicrocomputersandsmallcomputers.

Dualbusstructure

Inordertoeliminatethebottleneckofinformationtransmission,multiplesetsofbusesareoftensetup.Themostcommononeistosetupasetofdedicatedhigh-speedstoragebusesbetweenthemainmemoryandtheCPU.Theadvantageofthisstructureisthatthecontrolcircuitissimple,andthetransmissionrateoftheI\Obusislow;itsdisadvantageisthattheworkingefficiencyoftheCPUislow,becausetheinformationexchangebetweentheI/OdeviceandthemainmemoryiscarriedoutthroughtheCPU.Inthememory-centricdual-busstructure,themainmemorycanexchangeinformationwiththeCPUthroughthestoragebus,andcanalsoexchangeinformationwiththeI/Odevicethroughthesystembus.Theadvantageofthisstructureisthattheinformationtransmissionrateishigh;thedisadvantageisthatitneedsIncreasehardwareinvestment.

Large-scalesystemstructureusingchannels

Inordertoexpandthefunctionofthesystemandimprovetheefficiencyofthesystem,thechannelstructureisadoptedinlargeandmedium-sizedcomputersystems.Inthisstructure,ahostcanbeconnectedtomultiplechannels,achannelcanbeconnectedtooneormoreI/Ocontrollers,andanI/OcontrollercanbeconnectedtooneormoreI/Odevices,soIthasalargeroomforexpansion.Inaddition,thechannelmanagesandcontrolsI/Odevices,whichreducestheburdenontheCPUandimprovestheefficiencyoftheentiresystem.

Minimalhardwaresystem

Thehardwaredesignofanembeddedsystemdiffersdependingonitsapplicationandapplicationsystem.Undernormalcircumstances,userscanchoosetheappropriatemicroprocessortypeaccordingtotheirownrequirements,andmatchdifferenttypesofperipheralsaccordingtothecorrespondinginterfacecircuitstoformapplicationsystemsofdifferentpurposesanddifferentscales.Thesesystems,regardlessoftheirscale,canbedividedintothesmallestsystemcomposedofcorecircuitsandperipheralinterfacecircuitsrequiredbyvariousexternaldevicesfromthehardwarepointofview.Usuallythesmallesthardwaresystemreferstoacoresystemcomposedofaprocessor,SDRAMandFLASH,plussomenecessaryauxiliarycircuits.Theminimumhardwaresystemisnotonlythecorepartoftheentirehardwaresystem,butitscompositionalsohasanimportantimpactonthesoftwaresystem.ItscompositiondeterminesthedesignoftheBootloaderatthebottomofthesoftwaresystem,anditisalsothebasisforthenormaloperationoftheembeddedoperatingsystem.Inotherwords,thesmallesthardwaresystemandthelowestsoftwaresystemaboveitconstitutethemostbasicandcorepartoftheembeddedsystem.