HT82B42R datasheet(47/86 Pages) HOLTEK

47 / 86 page

Rev. 1.00

October 27, 2011

Rev. 1.00

October 27, 2011

HT82B42R/HT82B42RE

I/O MCU with USB Interface

USB Interface

Suspend Wake-Up and Remote Wake-Up

IfthereisnosignalontheUSBbusforover3ms,thedevicewillgointoasuspendmode.The

Suspendline(bit0oftheUSCregister)willbesetto"1"andaUSBinterruptistriggeredtoindicate

thatthedevicesshouldjumptothesuspendstatetomeetthe500μAUSBsuspendcurrentspec.

Inordertomeetthe500μAsuspendcurrent,thefirmwareshoulddisabletheUSBclockbyclearing

theUSBCKENbitwhichisbit3oftheSCCregisterto"0".Thesuspendcurrentis400μA.

Theusercanfurtherdecreasethesuspendcurrentto250μAbysettingtheSUSP2bitwhichisbit4

oftheSCCregister.IfintheUSBmodesetthisbitLVROPTmustdisable.

Whentheresumesignalissentoutbythehost,thedeviceswillwakeuptheMCUwithaUSB

interruptandtheResumeline(bit3oftheUSCregister)isset.Inordertomakethedevicefunction

properly,thefirmwaremustsettheUSBCKEN(bit3oftheSCCregister)to"1"andclearthe

SUSP2(bit4oftheSCCregister).SincetheResumesignalwillbeclearedbeforetheIdlesignal

issentoutbythehost,theSuspendline(bit0oftheUSCregister)willbesetto"0".Sowhenthe

MCUisdetectingtheSuspendline(bit0ofUSCregister),theResumelineconditionshouldbe

notedandtakenintoconsideration.

Afterfinishingtheresumesignal,thesuspendlinewillgoinactiveandaUSBinterruptwillbe

triggered.Thefollowingisthetimingdiagram.

SU SPEN D

US B Re su me S ig na l

US B_ IN T

Asthedevicehasaremotewakeupfunctionitcanwake-uptheUSBHostbysendingawake-up

pulsethroughRMOT_WK(bit1oftheUSCregister).OncetheUSBHostreceivesawake-up

signalfromthedevices,itwillsendaResumesignaltothedevice.Thetimingisasfollows:

SU SPEN D

U SB Re su me S ig na l

U SB_ IN T

RM OT _W K

Mi n. 1

US B CL K

Mi n. 2 .5 ms

HT82B42R Datasheet(PDF) 47 Page - Holtek Semiconductor Inc