Intel MCS 51 User Manual

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83C152 HARDWAREDESCRIPTION
PIN DESCRIPTION(Continued)
Pin #
Deeoription
DIP
PLCC(l)
1-8 4-11 Port l—Port 1 isan B-bitbidirectional1/0 portwithinternalpullups.Port1 pinsthat
have 1swrittento them are pulledhighbythe internalpullups,and inthat atatecan
be usedas inputs.Asinputs,Port1 pinsthat are externallybeingpulledIowwill
sourcecurrent(l[L,on the datasheet)becauseofthe internalpullups.
Port1 alsoservesthe functionsofvariousspecialfeaturesof the 8XC152, as listed
below:
Pin Name
Alternate Function
P1.o
GRXD
GSC date inputpin
P1.1
GTXD
GSCdate outputpin
P1.2
m
GSCenablesignalforan externaldfier
P1.3 TXC
GSC inputpinforexternaltransmitclock
P1.4 m GSC inputpinforexternalreceiveclock
P1.5
m
DMA holdinput/output
P1.6
HLDA
DMA holdacknowledgeinput/output
29-36
41-48 Port 2-Port 2 is an 8-bitbi-directionall/O portwithinternalpullups.Port2 pinsthat
have 1s writtento themare pulledhighbythe internalpullups,and inthatstate can
be usedas inputs.Asinputs,Port2 pinsthat are externallybeingpulledlowwill
sourcecurrent(lIL,onthe datasheet)becauseof the internalpullups.
Port2 emitsthe high-orderaddressbyteduringfetchesfromexternalProgram
Memoryif EBEN ispulledlow.Duringaccessesto externalDate Memorythat use
16-bitaddresees(MOVX @DPTRand DMA operations),Port2 emitstha high-order
addressbyte. In these applicationsituses stronginternalpullupswhenemitting1s.
Duringaccesses to externalDataMemorythat use8-bitaddresses(MOVX @Ri),
Port2 emitsthe contentsoftheP2 SpecialFunctionRegister.
Port2 also receivesthe high-orderaddressbiteduringprogramvetilcation.
10-17
14-16,
Port 3--Port 3 is an 8-bitbi-directional1/0 portwithinternalpullups.Port3 pinsthat
18,19,
have 1s writtento them are pulledhighbythe internalpullups,and inthatstatecan
23-25
be usedas inputs.Asinputs,Port3 pinsthat are externallybeingpulledlowwill
sourcecurrent([IL,onthe datasheet)becauseofthe pullupa.
Port3 also servesthefunctionsof variousspecialfeaturesofthe MCS-51 Family,
as listedbelow:
Pin Name
Alternate Function
P3.O RXD Serialinputline
P3.1 TXD Serialoutputline
P3.2 m
ExternalinterruptO
P3.3 INT1 Externalinterrupt1
P3.4 TO TimerOexternalinput
P3.5 T1
Timer 1 externalinput
P3.6 m
ExternalDataMemory
Writestrobe
P3.7 m
ExternalDataMemoryRead strobe
47-40
65-58 Port 4-Port 4 is an 8-bitbi-directional1/0 portwithinternalpullups.Port4 pinathat
have 1swrittento themare pulledhighbythe internalpullups,and inthatstate can
be usedes inputs.Asinputs,Port4 pinsthat are externallybeingpulledlowwill
Sourcecurrent(!IL,onthe datasheet)becauseof the internalpullups.Inaddition,
Port4 also receivesthe low-orderaddressbytesduringprogramverification.
NOTES:
1. N.C. pins on PLCCpackagemaybeconneotedtointernaldieandshouldnotbe usedincustomerapplications.
2. ItisraoommendedthatbothPin3 andPin33be groundedforPLCCdevices.
7-15

Intel MCS 51 Specifications

General

Brand	Intel
Model	MCS 51
Category	Microcontrollers
Language	English