Intel MCS 51 User Manual

i~.
HARDWARE DESCRIPTION OF THE 8051,8052 AND 80C51
Osc
[A I
‘ ICOJTROL’(5%’J:L’H‘F’k
INTERRUPT
270252-9
Figure 7. Timer/Counter 1 Mode O:13-BitCounter
(MSB] (LSB)
[
TFl
TRl TFo
TRO
IE1
IT1
IEO ITO
symbol POaltlon
Nelnesnds@meanm
TF1 TCON.7
llner 1 overflowFlag.Set by
hardware onTw/Counter overflow.
Cleared byherdwerewtten proc-
veetorsto intemuptroutine.
TR1 TmN.6 l%ner 1 Runeontml biLSet/cleared
by sottwsreto tumTkn6f/Counte?WI
off.
TFo TCON.5 Timer OovsrfiowFlag.Set by
herdwsreon Timef/Camter overflow.
Cleared byhsrdware whanpmmee.or
veetorsto intemuptmutine.
TRO TCON.4 Timer ORuncontml ML SatJcleared
byeoftwareto tum Timer/Counter on/
off,
-1
Posltlon
Neme mdslgnlffcenm
IE1 Tc%+J.3
Interrupt1 Edgsflsg.Sstbyhardwsre
whenexternalintenupt~ge
deteeted.Cfesmdwhen interrupt
prmeesed.
IT1 TCON.2 Intenupt1 Type mntrd bk Set/
elearadbyaofttnr
etoapecifyfsiiing
sdgdbw levelbiggwadesternel
interrupts.
IEO
TU)N.1
lntenuptOEdgsfleg. Set byhsrdwsre
whenexternal intsfruptedge
detected. Cleared * interrupt
~.
ITO TCON.O
InterruptOTyPSmntrol biLSet/
cleared bysdtwereto speeifyfslling
ed@k3wlevel tr@geredexternsl
interrupt
Figure 8.TCON:Timer/Counter Control Register
MODE 2
Timer Oin Mode3 establieheaTLOand THOas two
separatecounters.The logicfor Mode3 on Timer Ois
Mode2configurestheTimerregisterasan8-bitCoun-
sh_owninFigure10.TLO&estheTimerOcontrolbits:
ter
(’TLl)withautomatic reload, as shownin Figure 9.
Cfi, GATE,TRO,INTO,andTFO.THOislockedinto
OverfiowfromTL1not onlysetsTFl, but alsoreloads a timer function
(counting machine cycles)and takes
TL1 withthe contentsof THl, whichis presetby aoft-
overthe useofTR1and TFl fromTimer 1.Thus THO
ware. Thereloadleav~ THI unchanged. nowcontrolsthe “Timer 1“interrupt.
Mode2 operationis the same for Timer/CounterO. Mode 3 is providedfor applicationsrequiringan extra
8-bit timer or counter. With Timer o in Mode 3, gIL
MODE 3
8051ean
looklikeit has threeTimer/Counte~ and an
8052,like it has four. When Timer Ois in Mode 3.
Timer 1in Mode3simplyholdsits count.The effeetis
Tim~ 1eenbetinned on and offbyswitchingit out of
the ssrneas settingTRl = O.
and into its own Mode 3, or esn still be used by the
serial DOrtae s baud rate mnerstor, or in fact, in
any
appli~tion not requiring& iaterru~t.
3-11

Intel MCS 51 Specifications

General

Brand	Intel
Model	MCS 51
Category	Microcontrollers
Language	English