Holtek HT66F0175 - Page 47

Rev. 1.50 46 August 28, 2017 Rev. 1.50 47 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
IDLE1 Mode
TheIDLE1ModeisenteredwhenanHALTinstructionisexecutedandwhentheIDLENbitinthe
SMODregisterishighandtheFSYSONbitintheCTRLregisterishigh.IntheIDLE1Modethe
systemoscillatorwillbeinhibitedfromdrivingtheCPUbutmaycontinuetoprovideaclocksource
tokeepsomeperipheralfunctionsoperationalsuchastheWatchdogTimerandTMs.IntheIDLE1
Mode,thesystemoscillatorwillcontinuetorun,andthissystemoscillatormaybehighspeedorlow
speedsystemoscillator.
Control Registers
Asingleregister,SMOD,isusedforoverallcontroloftheinternalclockswithinthedevices.
SMOD Register
Bit 7 6 5 4 3 2 1 0
Name CKS2 CKS1 CKS0 FSTEN LTO HTO IDLEN HLCLK
R/W R/W R/W R/W R/W R R R/W R/W
POR 0 0 0 0 0 0 1 1
Bit7~5 CKS2~CKS0:SystemclockselectionwhenHLCLKis“0”
000:f
SUB
001:f
SUB
010:f
H
/64
011:f
H
/32
100:f
H
/16
101:f
H
/8
110:f
H
/4
111:f
H
/2
Thesethreebitsareusedtoselectwhichclockisusedasthesystemclocksource.In
additiontothesystemclocksource,whichcanbeeithertheLXTorLIRC,adivided
versionofthehighspeedsystemoscillatorcanalsobechosenasthesystemclock
source.
Bit4 FSTEN:FastWake-upControl(onlyforHXT)
0:Disable
1:Enable
ThisistheFastWake-upControlbitwhichdeterminesifthef
SUB
clocksourceis
initiallyusedafterthedevicewakesup.Whenthebitishigh,thef
SUB
clocksourcecan
beusedasatemporarysystemclocktoprovideafasterwakeuptimeasthef
SUB
clock
isavailable.
Bit3 LTO :Lowspeedsystemoscillatorreadyag
0:Notready
1:Ready
Thisisthelowspeedsystemoscillatorreadyagwhichindicateswhenthelowspeed
systemoscillatorisstableafterpoweronresetorawake-uphasoccurred.Theag
willbelowwhenintheSLEEP0Modebutafterawake-uphasoccurred,theagwill
changetoahighlevelafter128clockcyclesiftheLXToscillatorisusedand1~2
clockcyclesiftheLIRCoscillatorisused.