Holtek BS82B12A-3 - Page 60

Rev. 1.20 60 January 23, 2015 Rev. 1.20 61 January 23, 2015
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
BS82B12A-3/BS82C16A-3/BS82D20A-3
Touch Key 8-Bit Flash MCU with LED/LCD Driver
Low Voltage Reset – LVR
Themicrocontrollercontainsalowvoltageresetcircuitinordertomonitorthesupplyvoltageofthe
device.TheLVRfunctionisalwaysenabled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CTRLregisterwill
alsobesethigh.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
specied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xedatavoltagevalueof2.55V.NotethattheLVRfunctionwillbe
automaticallydisabledwhenthedeviceenterstheSLEEPorIDLEmode.

    

  


Note:t
RSTD
ispower-ondelay,typicaltime=50ms
Low Voltage Reset Timing Chart
• CTRL Register
Bit 7 6 5 4 3 2 1 0
Name FSYSON — HIRCS1 HIRCS0 LXTLP LVRF D1 WRF
R/W R/W — R/W R/W R/W R/W R/W R/W
POR 0 — 0 0 0 x 0 0
"x"
unknown
Bit7 FSYSON:f
SYS
ControlinIDLEMode
Describeelsewhere
Bit6 Unimplemented,readas"0".
Bit5~4 HIRCS1~HIRCS0:HIRCfrequencyclockselect
Describeelsewhere
Bit3 LXTLP:LXTlowpowercontrol
Describeelsewhere
Bit2 LVRF:LVRfunctionresetag
0:Notoccur
1:Occurred
ThisbitissethighwhenaspecicLowVoltageResetsituationconditionoccurs.This
bitcanonlybeclearedtozerobytheapplicationprogram.
Bit1 Undenedbit
Thisbitcanbereadorwrittenbyusersoftwareprogram
Bit0 WRF:WDTControlregistersoftwareresetag
Describeelsewhere
Watchdog Time-out Reset during Normal Operation
TheWatchdogtime-outResetduringnormaloperationisthesameasaLVRresetexceptthatthe
Watchdogtime-outagTOwillbesetto"1".

  


 
    
Note:t
RSTD
ispower-ondelay,typicaltime=16.7ms
WDT Time-out Reset during Normal Operation Timing Chart