HT16L21 datasheet(21/36 Pages) HOLTEK

21 / 36 page

Rev. 1.00

November 16, 2011

HT16L21

SPI Serial Interface

SPI Operation

Thedevicealsoincludesa3-wireSPIserialinterface.TheSPIoperationsaredescribedasfollows:

• TheCSBpinisusedtoactivatethedatatransfer.WhentheCSBpinisatahighlevel,theSPIoperationwillbe

resetandstopped.IftheCSBpinchangesstatefromhightolow,datatransmissionwillstart.

• ThedataistransferredfromtheMSBofeachbyteandisshiftedintotheshiftregisteroneachCLKrisingedge.

• Theinputdataisautomaticallylatchedintotheinternalregisterforeach8-bitinputdataaftertheCSBsignal

goeslow.

• Forreadoperations,theMCUshouldassertahighpulseontheCSBpintochangethedatatransferdirection

frominputmodetooutputmodeontheDIOpinaftersendingthecommandbyteandthesettingvalues.Ifthe

MCUsetstheCSBsignaltoahighlevelagainafterreceivingtheoutputdata,thedatadirectionontheDIOpin

willbechangedintoinputmodeandthereadoperationwillend.

• Forareadoperation,thedataisoutputontheDIOpinattheCLKfallingedge.

• FordisplayRAMdataread/writeoperationsusingtheSPIinterface,theread/writecontrolbitiscontainedin

theDisplayDataInputCommand.RefertotheDisplayDataInputCommanddescriptionformoredetails.

SPI Interface Write Operation

Byte Write Operation

• Single Command Type

ASingleCommandwriteoperationisactivatedbytheCSBsignalgoinglow.The8-bitcommandbyteis

shiftedfromtheMSBintotheshiftregisterateachCLKrisingedge.

BIT7

CSB

CLK

DIO

Command byte

BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0

SPI Single Command Type Write Operation

• Compound Command Type

Foracompoundcommand,an8-bitcommandbyteisfirstshiftedintotheshiftregisterfollowedbyan8-bit

commandsetting.NotethattheCLKhighpulsewidth,afterthecommandbytehasbeenshiftedin,must

remainatthislevelforatleast2μsafterwhichthecommandsettingdatacanbeconsecutivelyshiftedin.

CSB

CLK

DIO

Command byte

Command setting

Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1

2μs(min)

Bit6 Bit5 Bit4 Bit3 Bit2 Bit1

Bit7

Bit0

SPI Compound Command Type Write Operation

HT16L21 Datasheet(PDF) 21 Page - Holtek Semiconductor Inc

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