HT16L21 datasheet(23/36 Pages) HOLTEK

23 / 36 page

Rev. 1.00

November 16, 2011

HT16L21

SPI Interface Display RAM Read Operation

Inthismode,themasterreadsthedevicedataaftersendingtheDisplayDataInputcommandwhentheCSBpin

changesstatefromhightolow.Followingtheread/writecontrolbit,whichiscontainedintheDisplayDataInput

command,istheregisteraddressbytewhichiswrittentotheinternaladdresspointer.Afterthestartaddressofthe

ReadOperationhasbeenconfigured,anotherCSBhighpulseisplacedonthebusandthentheMSBofthedata

whichwasaddressedistransmittedfirstontheSPIbus.Theaddresspointerisonlyincrementedby1afterthe

receptionofeachdatabyte.ThatmeansthatifthedeviceisconfiguredtotransmitthedataattheaddressofAN+1,

themasterwillreadthetransferreddatabyteandtheaddresspointerisincrementedtoAN+2.Aftertheinternal

addresspointerreachesthemaximummemoryaddress,theaddresspointerwillberesetto00H.

ThiscycleofreadingconsecutiveaddresseswillcontinueuntilthemasterpullstheCSBlinetoahighlevelto

terminatethedatatransfer.

A3 A2 A1 A0

D7 D6 D5 D4 D3 D2 D1 D0

CSB

CLK

DIO

1st data

Display data Input command byte

D7 D6 D5 D4 D3 D2 D1 D0

2nd data

3rd data

2μs(min)

Data byte

Data

byte

Data byte

D7 D6 D5 D4 D3 D2 D1 D0

Nth data

Data byte

(N-1)th

data

2μs(min)

CSB

CLK

DIO

SPI Interface N Bytes Display RAM Data Read Operation

HT16L21 Datasheet(PDF) 23 Page - Holtek Semiconductor Inc