Pin configuration of 8051 Microcontroller.pdf

The pin diagram of 8051 microcontroller consists of 40 pins.

1. Pin diagram of 8051
Mrs. Hezal Lopes
Assistant Professor
DJSCE,VileParle(W)

2. •Pin configurationof 8051

4. •Thepindiagramof8051microcontrollerconsistsof40pinsasgivenbelow:
•Pin1-8(Port1):
•Theseare8-bitbidirectionalI/Oportwithinternalpull-upresisters.
•Itdoesnotperformanytask;itisjustanI/Oport
•Pin9(RST):
•ItisaResetinputpinwhichisusedtoresetthemicrocontrollertoitsinitialposition.
•Pin10to17(Port3):
•Itisalsoan8-bitbidirectionalI/Oportwithinternalpull-upresisters.
•Additionally,itperformssomespecialfunctions:

5. PORT 3
Pin
Function Description
P3.0 RXD SerialInput
P3.1 TXD SerialOutput
P3.2 INT0 ExternalInterrupt0
P3.3 INT1 ExternalInterrupt1
P3.4 T0 Timer0
P3.5 T1 Timer1
P3.6 WR ExternalMemoryWrite
P3.7 RD ExternalMemoryRead

6. •Pin18and19:
•ItisXTAL1andXTAL1pinsrespectively.
•Thesepinsareusedforconnectinganexternalcrystaltogetthesystemclock.
•Pin20(GND):
•Itisagroundpin.
•Thispinisconnectedtothegroundandservesasthereferencevoltageforthemicrocontroller.
•Pin21to28(Port2):
•ThesepinsarebidirectionalI/Oport.
•Higherorderaddressbussignalsaremultiplexedwiththisbidirectionalport.
•Pin29(PSEN):
•ItisaProgramStoreEnablePin.
•UsingthisPSENpinexternalprogrammemorycanberead.

7. •Pin30(ALE/PROG):
•ThispinistheAddressLatchEnablepin.
•Itisinput,active-highpin.
•Thispinisusedtodistinguishbetweenmemorychipswhenmultiplememorychipsareused.
•Duringflashprogrammingi.e.ProgrammingofEPROM,thispinactsasprogrampulseinput(PROG).
•Pin31(EA/VPP):
•NamedasexternalAccessEnablePin(EA).
•Itisusedtoenableordisabletheexternal(ROM)programmemoryinterfacing.
•VPP:Itreceives12Vprogrammingenablevoltageduringflashmemoryprogrammingforchipsthatrequires12VVPP.

8. •Pin32-39(Port0):
•ThesearealsoabidirectionalI/Opinsbutwithoutanyinternalpull-ups.
•Hence,itrequiresexternalpinsinordertouseport0pinsasI/Oport.
•Lowerorderdataandaddressbussignalsaremultiplexedwiththisport.
•Pin40(VCC):
•Thispinisusedtosupply+5Vvoltagepowertothecircuit.

9. Thank You