intel.
87C51GBHARDWARE DESCRIPTION
Table26.PCON:PowerControlRe9ieter
PCON
Address= 87H
ResetValue= OOXXOOOOB
NotBitAddressable
SMOD1SMODO — ] POF
GF1
GFO PD IDL
Bit 7 6 5
4 3
2 1
0
Symbol Function
SMOD1 DoubleBaudratebit.Whensettoa 1andTimer1isused
to generate baud rates, and the
Serial
Portisusedinmodes1,2,or3.
SMODO Whenset,Read/WriteacceasestoSCON.7aretotheFEbit.Whenclear,Read/Write
accessestoSCON.7aretotheSMObit.
—
Notimplemented,reservedforfutureuse.*
POF PowerOffFlag.SetbyhardwareonthetisingedgeofVCC.Setorclearedbysoftware.This
flagallowsdetectionofapowerfailurecausedreset.VcCmustremainabove3Vtoretain
thisbit.
GF1
Generel-purpoeeflagbit.
GFO
General-purposeflagbit.
PD PowerDownbit.SettingthisbitactivatesPowerDown
operation.
IDL
Idlemodebit.Settingthisbt activatesidlemodesoperation.
If1sarewrittentoPDandIDLatthesametime,PDtakesprecedence.
NOTE
*UeersoftwareshouldnotwriteIstounimplementedbits.
These bite maybe usedinfutureS051 familyproduotsto
invokenew features. In that case, the reset or inactivevalue of the new bhwillbe O,and itsactive valuewill be 1.
The valueread froma raeerv
ad bil is indeterminate.
o
KI
m
xTAL 2 s X7AL 1
Oac
INTSRRUPT,
DSSRIALPORT,
TIMER SLOCKS
E
Cw
=
270S97-36
Figure36.IdleandPowerDownHardware
6-50
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