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7COMMUNICATIONS
7.1I
2
CINTERFACE
(a)1-bytewrite (b)quickread
(c)1-byteread
(d)incrementalread
(S=Start,Sr=RepeatedStart, A = Acknowledge,N=No Acknowledge,andP =Stop).
FuelGaugeGenerated
Hostgenerated
bq27500
bq27501
System-SideImpedanceTrack™FuelGauge
SLUS785–SEPTEMBER2007
ThefuelgaugesupportsthestandardI
2
Cread,incrementalread,one-bytewritequickread,and
functions.The7-bitdeviceaddress(ADDR)isthemostsignificant7bitsofthehexaddressandisfixedas
1010101.The8-bitdeviceaddressistherefore0xAAor0xABforwriteorread,respectively.
Figure7-1.SupportedI
2
CFormats
Thequickreadreturnsdataattheaddressindicatedbytheaddresspointer.Theaddresspointer,a
registerinternaltotheI
2
Ccommunicationengine,incrementswheneverdataisacknowledgedbythe
bq27500ortheI
2
Cmaster.Quickwritesfunctioninthesamemannerandareaconvenientmeansof
sendingmultiplebytestoconsecutivecommandlocations(suchastwo-bytecommandsthatrequiretwo
bytesofdata).
Attempttowritearead-onlyaddress(NACKafterdatasentbymaster):
Attempttoreadanaddressabove0x7F(NACKcommand):
Attemptatincrementalwrites(NACKallextradatabytessent):
Incrementalreadatthemaximumallowedreadaddress:
TheI
2
CenginereleasesbothSDAandSCLiftheI
2
Cbusisheldlowfort
(BUSERR)
.Ifthefuelgaugewas
holdingthelines,releasingthemfreesthemastertodrivethelines.Ifanexternalconditionisholding
eitherofthelineslow,theI
2
Cengineentersthelow-powersleepmode.
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