Intel MCS 51 User Manual

intd.
87C51GB HARDWARE DESCRIPTION
6.6 A/D in Power Down
The AfD on the 8XC51GBcontainscircuitrythat lim-
its the amount of current dissipated during Power
Downmodeto leakagecurrent only.For this circuitry
to tknction properly, AV~ should be tied to VW
during powerdown.The IpD specificationin the data
sheet includesthe current for the entire chip. While
AV~ is tiedto Vw duringPowerDown,thevoltage
may be reducedto the minimumvoltageas shownin
the data sheet.
7.0 PROGRAMMABLECOUNTER
ARRAY
ProgrammableCounter Arrays (PCAS)providemore
timingcapabilitieswith leasCPU interventionthan the
standard timer/cmsnters.Their advantagesincludere-
duced sofiwareoverheadand improved
accuracy.For
exampl%a PCA can provide better resolution than
Timers O,1,and 2 becausethe PCA clock rate can be
three timesfa6ter.A PCA can dSOpSSfOrMMSXlyt@S
that these hardwaretimers cannot (i.e. measurephase
differencesbetweensignalsor generatePWM6).
The 8XC51GBhas two PCAs called PCA and PCA1.
The followingtext and figures address only PCA but
are also applicableto PCA1 with the followingexcep-
tions:
1.PCA1, Module 4 does not support the Watchdog
Timer
2. All the SFRsand bits have 1sadded to their names
(seeTable 11).
3. Port 4 k the interfacefor PCA1:
P4.2 ECI1
P4.3 CIEX1
P4.4
CIEX2
P4.5
C1EX2
P4.6
C1EX3
P4.7
C1EX4
Table11.PCAandPCA1SFRS
PCA
PCAI
SFRS:
CCON.. . . . . . . . . . . . . . . . ... .. CICON
CMOD. . . .. .. .. .. .. . .. . . . . . . CIMOD
CCAPMO. . . . .. .. .. . .. .. . . . . CICAPMO
CCAPM1.. . . . . . . . . . . . . .. .. . CICAPM1
CCAPM2.. . . . . . . . . . . . . .. .. . C1CAPM2
CCAPM3.. . . . . . . . . . . . . .. ... C1CAPM3
CCAPM4.. . . . . . . . . . . . . .. ... C1CAPM4
CL . . .. .. .. .. .. . .. . . . . . . . . . . CL1
CCAPOL. . . . . .. . .. .. .. .. . . . . CICAPOL
CCAPIL. .. .. .. . .. .. . . . . . . . . CICAPIL
CCAP2L. .. .. .. . ... . . . . . . . . . C1CAP2L
CCAP3L. .. .. .. . .. .. . . . . . . . . C1CAP3L
CCAP4L. .. .. .. . .. . .. . . . . . . . C1CAP4L
CH. ... . ... . . . . . . . . . . . . . . . .. CH1
CCAPOH.. ... . .. . . . . .. .. . . . . CICAPOH
CCAPIH.. . . . . . . . . . . . . .. .... CICAP1H
CCAP2H.. . . . . . . . . . . . . .. .... C1CAP2H
CCAP3H. . .. .. .. .. . .. . . . . . . . C1CAP3H
CCAP4H. . ... . .. .. . .. . .. .... C1CAP4H
BITS:
ECI. . . . . . .. . ... . .. . . .. . . . . . . ECI1
CEXO.. . . . . . . . . . . . . . . . ... ... CIEXO
CEX1.. . ... . .. .. . . . . . . . . . . . . CIEX1
CEX2.. . ... . .. .. . . . . .. . . . ... C1EX2
CEX3.. . ... . .. .. . . . . . . . . . . . . C1EX3
CEX4.. . .. .. .. .. . . . . .. ..... . C1EX4
CCFO.... . .. . . . . . . . . .. . . . ... CICFO
CCF1.. . .. .. ... . . . . . .. .. . . .. CICF1
CCF2.. . ... . .. .. . . . . .. .. . . . . C1CF2
CCF3.. . .. .. .. .. . . . . .. ..... . C1CF3
CCF4. .. .. .. .. .. . . . . .. .... .. C1CF4
CR. .. .. .. .. .. . . . . . . . . . . . . . . CR1
CF
. .. .. .. .. .. . . . . . . . . . . . . . . CF1
16 BITSEACH
-“3’’”0
I
P1.4/cExl
16 B17S
P1.5/CEX2
t-@--’’cEx3Ex3
P1.7/CEX4
270S97-19
I%gure17.PCABlockDiagram
6-23

Intel MCS 51 Specifications

General

Brand	Intel
Model	MCS 51
Category	Microcontrollers
Language	English