Holtek HT66F002 - Low Voltage Reset - LVR

Rev. 1.71 50 April 11, 2017 Rev. 1.71 51 April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
MoreinformationregardingexternalresetcircuitsislocatedinApplicationNoteHA0075Eonthe
Holtekwebsite.
PullingtheRESPinlowusingexternalhardwarewillalsoexecuteadevicereset.Inthiscase,asinthe
caseofotherresets,theProgramCounterwillresettozeroandprogramexecutioninitiatedfromthispoint.

    




     
Note:t
RSTD
ispower-ondelay,typicaltime=16.7ms
RES Reset Timing Chart
• RSTC External Reset Register – HT66F002/HT66F003
Bit 7 6 5 4 3 2 1 0
Name RSTC7 RSTC6 RSTC5 RSTC4 RSTC3 RSTC2 RSTC1 RSTC0
R/W R/W R/W R/W R/W R R R/W R/W
POR 0 1 0 1 0 1 0 1
Bit7~0 RSTC7 ~ RSTC0:PA7/RESselection
01010101:conguredasPA7pinorotherfunction
10101010:conguredasRESpin
OtherValues:Inhibittouse
AllresetwillresetthisregisterasPORvalueexceptWDTtimeoutHardwarewarmreset.
• RSTC External Reset Register – HT66F004
Bit 7 6 5 4 3 2 1 0
Name RSTC7 RSTC6 RSTC5 RSTC4 RSTC3 RSTC2 RSTC1 RSTC0
R/W R/W R/W R/W R/W R R R/W R/W
POR 0 1 0 1 0 1 0 1
Bit7~0 RSTC7 ~ RSTC0:PC2/RESselection
01010101:ConguredasPC2pinorotherfunction
10101010:Conguredas

RES

pin
OtherValues:Inhibittouse
AllresetwillresetthisregisterasPORvalueexceptWDTtimeoutHardwarewarmreset.
Low Voltage Reset – LVR
Themicrocontrollercontainsalowvoltageresetcircuitinordertomonitorthesupplyvoltageof
thedeviceandprovideanMCUresetshouldthevaluefallbelowacertainpredenedlevel.The
LVRfunctionisalwaysenabledduringthenormalandslowmodeswithaspecicLVRvoltage
V
LVR
.Ifthesupplyvoltageofthedevicedropstowithinarangeof0.9V~V
LVR
suchasmightoccur
whenchangingthebattery,theLVRwillautomaticallyresetthedeviceinternallyandtheLVRF
bitintheSMOD1registerwillalsobesetto1.ForavalidLVRsignal,alowvoltage,i.e.,avoltage
intherangebetween0.9V~V
LVR
mustexistforgreaterthanthevaluet
LVR
specifiedintheA.C.
characteristics.Ifthelowvoltagestatedoesnotexceedthisvalue,theLVRwillignorethelow
supplyvoltageandwillnotperformaresetfunction.TheactualV
LVR
is2.1V,theLVRwillresetthe
deviceafter2~3LIRCclockcycles.NotethattheLVRfunctionwillbeautomaticallydisabledwhen
thedeviceenterstheSLEEP/IDLEmode.

    

  


Note:t
RSTD
ispower-ondelay,typicaltime=50ms
Low Voltage Reset Timing Chart