HT68F20 datasheet(162/210 Pages) HOLTEK

162 / 210 page

HT68F20/HT68F30/HT68F40/HT68F50/HT68F60

Rev. 1.00

162

November 3, 2009

Interrupt Wake-up Function

Each of the interrupt functions has the capability of wak-

ing up the microcontroller when in the SLEEP or IDLE

Mode. A wake-up is generated when an interrupt re-

quest flag changes from low to high and is independent

of whether the interrupt is enabled or not. Therefore,

even though the device is in the SLEEP or IDLE Mode

and its system oscillator stopped, situations such as ex-

ternal edge transitions on the external interrupt pins, a

low power supply voltage or comparator input change

may cause their respective interrupt flag to be set high

and consequently generate an interrupt. Care must

therefore be taken if spurious wake-up situations are to

be avoided. If an interrupt wake-up function is to be dis-

abled then the corresponding interrupt request flag

should be set high before the device enters the SLEEP

or IDLE Mode. The interrupt enable bits have no effect

on the interrupt wake-up function.

Programming Considerations

By disabling the relevant interrupt enable bits, a re-

quested interrupt can be prevented from being serviced,

however, once an interrupt request flag is set, it will re-

main in this condition in the interrupt register until the

corresponding interrupt is serviced or until the request

flag is cleared by the application program.

Where a certain interrupt is contained within a

Multi-function interrupt, then when the interrupt service

routine is executed, as only the Multi-function interrupt

request flags, MF0F~MF5F, will be automatically

cleared, the individual request flag for the function

needs to be cleared by the application program.

It is recommended that programs do not use the

²CALL²

instruction within the interrupt service subroutine. Inter-

rupts often occur in an unpredictable manner or need to

be serviced immediately. If only one stack is left and the

interrupt is not well controlled, the original control se-

quence will be damaged once a CALL subroutine is exe-

cuted in the interrupt subroutine.

Every interrupt has the capability of waking up the

microcontroller when it is in SLEEP or IDLE Mode, the

wake up being generated when the interrupt request

flag changes from low to high. If it is required to prevent

a certain interrupt from waking up the microcontroller

then its respective request flag should be first set high

before enter SLEEP or IDLE Mode.

As only the Program Counter is pushed onto the stack,

then when the interrupt is serviced, if the contents of the

accumulator, status register or other registers are al-

tered by the interrupt service program, their contents

should be saved to the memory at the beginning of the

interrupt service routine.

To return from an interrupt subroutine, either a RET or

RETI instruction may be executed. The RETI instruction

in addition to executing a return to the main program

also automatically sets the EMI bit high to allow further

interrupts. The RET instruction however only executes a

return to the main program leaving the EMI bit in its

present zero state and therefore disabling the execution

of further interrupts.

HT68F20 Datasheet(PDF) 162 Page - Holtek Semiconductor Inc

HT68F20 Datasheet(HTML) 162 Page - Holtek Semiconductor Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL