Holtek HT66F0175 - Page 168

Rev. 1.50 168 August 28, 2017 Rev. 1.50 169 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
UART Interrupt Structure
SeveralindividualUARTconditionscangenerateaUARTinterrupt.Whentheseconditionsexist,
alowpulsewillbegeneratedtogettheattentionofthemicrocontroller.Theseconditionsarea
transmitterdataregisterempty,transmitteridle,receiverdataavailable,receiveroverrun,address
detectandanRXpinwake-up.Whenanyoftheseconditionsarecreated,ifitscorresponding
interruptcontrolisenabledandthestackisnotfull,theprogramwilljumptoitscorresponding
interruptvectorwhereitcanbeservicedbeforereturningtothemainprogram.Fourofthese
conditionshavethecorrespondingUSRregisteragswhichwillgenerateaUARTinterruptifits
associatedinterruptenablecontrolbitintheUCR2registerisset.Thetwotransmitterinterrupt
conditionshavetheirowncorrespondingenablecontrolbits,whilethetworeceiverinterrupt
conditionshaveasharedenablecontrolbit.Theseenablebitscanbeusedtomaskoutindividual
UARTinterruptsources.
Theaddressdetectcondition,whichisalsoaUARTinterruptsource,doesnothaveanassociated
flag,butwillgenerateaUARTinterruptwhenanaddressdetectconditionoccursifitsfunction
isenabledbysettingtheADDENbitintheUCR2register.AnRXpinwake-up,whichisalsoa
UARTinterruptsource,doesnothaveanassociatedag,butwillgenerateaUARTinterruptifthe
microcontrolleriswokenupfromIDLE0orSLEEPmodebyafallingedgeontheRXpin,ifthe
WAKEandRIEbitsintheUCR2registerareset.NotethatintheeventofanRXwake-upinterrupt
occurring,therewillbeacertainperiodofdelay,commonlyknownastheSystemStart-upTime,for
theoscillatortorestartandstabilizebeforethesystemresumesnormaloperation.
NotethattheUSRregisterflagsarereadonlyandcannotbeclearedorsetbytheapplication
program,neitherwilltheybeclearedwhentheprogramjumpstothecorrespondinginterrupt
servicingroutine,asisthecaseforsomeoftheotherinterrupts.Theflagswillbecleared
automaticallywhencertainactionsaretakenbytheUART,thedetailsofwhicharegiveninthe
UARTregistersection.TheoverallUARTinterruptcanbedisabledorenabledbytherelated
interruptenablecontrolbitsintheinterruptcontrolregistersofthemicrocontrollertodecidewhether
theinterruptrequestedbytheUARTmoduleismaskedoutorallowed.
USR Register
Transmitter Empty Flag TXIF
0
1
WAKE
Interrupt
signal to MCU
Transmitter Idle Flag TIDLE
Receiver Overrun Flag
OERR
Receiver Data Available
RXIF
RX Pin
Wake-up
UCR2 Register
OR
0
1
ADDEN
0
1
RIE
0
1
TIIE
0
1
TEIE
0
1
RX7 if BNO=0
RX8 if BNO=1
UCR2 Register
UART Interrupt
Request Flag
URF
0
1
URE
0
1
EMI
UART Interrupt Structure