Rev. 1.00

21

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

Bit6 Bit5 Bit4 Bit3 Bit2 Bit1

Bit7

Bit0

Bit0

SPI Compound Command Type Write Operation