标签: io扩展

GPIOexpandersprovideeasyI/Oexpansionusingstandardserialinterfaces.GPIOproductsareusedtoincreasetheI/OonanMCUorprovideremoteI/Ousingaserialinterface.ThisapplicationnotediscussesthefeaturesetanduseoftheMCP23X08/17(8-bitand16-bit)GPIOExpand-ers.TheMCP23X08are8-bitGPIOExpanders:•MCP23008:I2C™Interface•MCP23S08:SPIInterfaceTheMCP23X17are16-bitGPIOExpanders:•MCP23017:I2CInterface•MCP23S17:SPIInterfaceThefunctionsandfeaturesoftheMCP23X08andMCP23X17arebasicallythesame,exceptwhereotherwisenoted.AN1043UniqueFeaturesoftheMCP23X08/17GPIOExpandersAuthor:PatRichardsI/OPORTDESCRIPTIONMicrochipTechnologyInc.TheI/Oportishighlyconfigurableformaximumflexibility.Figure1isasimplifiedblockdiagramofanINTRODUCTIONI/Oportpin.Theportcaneitherdrivelogiclevelsonthepin,orreadlogiclevelsfromthepad.ThelevelontheGPIOexpandersprovideeasyI/Oexpansionusingpadcanbereadatanytime,regardlessifthepinisstandardser……

ThisapplicationnotedescribeshowtouseaPIC16F877AasanI2C™mastertocommunicatewiththeMicrochipMCP23016I2CI/OExpanderslavedevice.AnI/OExpanderdeviceisusedtoincreasetheI/Ocapabilityofamicrocontroller(refertoFigure1).Amicrocontroller’sI2Cportcanbeusedasacommuni-cationchannelwithMCP23016(s)toexpandthemicro-controller’sI/Ocount.ByusingtwoI2Cpins(andonegeneral-purposeI/Opin,ifusingtheinterruptcapabilityoftheMCP23016),16to128general-purposeI/Oscanbegained.TheMCP23016hasthreeaddresspinswhichcanbeusedtoprovideuniqueaddressesforuptoeightdevices.EachdeviceattachedtotheI2Cbusmustbeassignedauniqueaddressunlessalldevices(withthesameaddress)arereceivingthesamedataanddonottrans-mitanydata.Whenthemasterinitiatesadatatransfer,theaddressoftheslavedeviceistransmitted.Withintheaddress,theLSb(R/Wbit)specifieswhetherthemasterreadsfrom,orwritesto,theslave.Forwriteoperations,aseriesofbyteswouldbetransmittedfromthemaster.Forreadoperations,themasterwaitsforthebustobefree(i.e.,SCLlinenotpulledlow)andthenclocksthedatatobereceivedfromtheslave.MAN245InterfacingTheMCP23016I/OExpanderWithThePIC16F877AWhatcanyoudowithanI/OExpander?Author:AbdelwahabFassi-FihriMicrochipTechnologyInc.AnI/OExpandercanalsobeusedtomonitorswitchesand/orsensors,driveLEDsand/orrelays,aswellasothergeneral-purposeI/Ofunctions.AnI/OExpanderINTRODUCTIONcanhaveseveralusesinavarietyofapplications.Typ-This……