Holtek HT66F0175 - Page 119

Rev. 1.50 118 August 28, 2017 Rev. 1.50 119 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
A/D Converter Control Registers – SADC0, SADC1, SADC2, ACERL
TocontrolthefunctionandoperationoftheA/Dconverter,threecontrolregistersknownasSADC0,
SADC1andSADC2areprovided.These8-bitregistersdenefunctionssuchastheselectionof
whichanalogchannelisconnectedtotheinternalA/Dconverter,thedigitiseddataformat,the
A/DclocksourceaswellascontrollingthestartfunctionandmonitoringtheA/Dconverterbusy
status.Asthesedevicescontainonlyoneactualanalogtodigitalconverterhardwarecircuit,each
oftheexternalandinternalanalogsignalsmustberoutedtotheconverter.TheSACS2~SACS0
bitsintheSADC0registerareusedtodeterminewhichexternalchannelinputisselectedtobe
converted.TheSAINS2~SAINS0bitsintheSADC1registerareusedtodeterminethattheanalog
signaltobeconvertedcomesfromtheinternalanalogsignalorexternalanalogchannelinput.Ifthe
SAINS2~SAINS0bitsaresetto“000”or“100”,theexternalanalogchannelinputwillbeselected
tobeconvertedandtheSACS2~SACS0bitscandeterninewhichexternalchannelisselectedto
beconverted.IftheSAINS2~SAINS0bitsaresettoanyothervaluesexcept“000”and“100”,one
oftheinternalanalogsignalscanbeselectedtobeconverted.Theinternalanalogsignalscanbe
derivedfromtheA/Dconvertersupplypower,V
DD
,orinternalreferencevoltage,V
R
,withaspecic
ratioof1,1/2or1/4.Iftheinternalanalogsignalisselectedtobeconverted,theexternalchannel
signalinputwillautomaticallybeswitchedofftoavoidthesignalcontention.
SAINS [2:0] SACS [2:0] Input Signals Description
000, 100 000~111 AN0~AN7 External channel analog input
001 xxx V
DD
A/D converter power supply voltage
010 xxx V
DD
/2 A/D converter power supply voltage/2
011 xxx V
DD
/4 A/D converter power supply voltage/4
101 xxx V
R
Internal reference voltage
110 xxx V
R
/2 Internal reference voltage/2
111 xxx V
R
/4 Internal reference voltage/4
A/D Converter Input Signal Selection
TheanaloginputpinfunctionselectionbitsintheACERLregisterdeterminewhichpinsonI/O
PortsareusedasexternalanalogchannelsfortheA/Dconverterinputandwhichpinsarenottobe
usedastheA/Dconverterinput.WhenthepinisselectedtobeanA/Dinput,itsoriginalfunction
whetheritisanI/Oorotherpin-sharedfunctionswillberemoved.Inaddition,anyinternalpull-
highresistorconnectedtothepinwillbeautomaticallyremovedifthepinisselectedtobeanA/D
converterinput.