HT16L21 datasheet(18/36 Pages) HOLTEK

18 / 36 page

Rev. 1.00

November 16, 2011

HT16L21

Acknowledge

• Eachbytesofeightbitsisfollowedbyoneacknowledgebit.ThisAcknowledgebitisalowlevelplacedonthe

busbythereceiver.Themastergeneratesanextraacknowledgerelatedclockpulse.

• AslavereceiverwhichisaddressedmustgenerateanAcknowledge,ACK,afterthereceptionofeachbyte.

• ThedevicethatacknowledgesmustpulldowntheSDAlineduringtheacknowledgeclockpulsesothatit

remainsstablelowduringthehighperiodofthisclockpulse.

• Amasterreceivermustsignalanendofdatatotheslavebygeneratinganot-acknowledge,NACK,bitonthe

lastbytethathasbeenclockedoutoftheslave.Inthiscase,themasterreceivermustleavethedatalinehigh

duringthe9thpulsetonotacknowledge.ThemasterwillgenerateaSTOPorrepeatedSTARTcondition.

clockpulsefor

acknowledgement

DataOutput

byTransmitter

DataOutptu

byReceiver

SCLFrom

Master

acknowledge

notacknowledge

START

condition

Slave Addressing

• TheslaveaddressbyteisthefirstbytereceivedfollowingtheSTARTconditionformthemasterdevice.The

firstsevenbitsofthefirstbytemakeuptheslaveaddress.Theeighthbitdefinesareadorwriteoperationtobe

performed.WhentheR/Wbitis“1”,thenareadoperationisselected.A“0”selectsawriteoperation.

• TheHT16L21deviceaddressbitsare“0111000”.Whenanaddressbyteissent,thedevicecomparesthefirst

sevenbitsaftertheSTARTcondition.Iftheymatch,thedeviceoutputsanAcknowledgeontheSDAline.

Slave Address

R/W

MSB

LSB

HT16L21 Datasheet(PDF) 18 Page - Holtek Semiconductor Inc