HT56RB27 datasheet(87/153 Pages) HOLTEK

87 / 153 page

Essentially operating as a programmable timer, when the Time Base overflows it will set a Time Base

interrupt flag which will in turn generate an Interrupt request via the Multi-function 0 Interrupt vector.

Programming Considerations

By disabling the interrupt enable bits, a requested interrupt can be prevented from being serviced,

however, once an interrupt request flag is set, it will remain in this condition in the INTC0, INTC1,

INTC2, MFIC0 and MFIC1 registers 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, 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. Interrupts 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 sequence will be

damaged once a CALL subroutine is executed 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 micro controller then its respective request

flag should be first set high before entering the 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 altered 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

²RET² or ²RETI² instruction may be executed.

The

²RETI² instruction in addition to executing a return to the main program also automatically sets

the EMI bit high to allow further interrupts. The

²RET² 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.

HT56RB27

TinyPowerTM A/D Type Smart Card OTP MCU

with DAC, ISO 7816 and USB Interfaces

Rev. 1.20

April 26, 2013

f S S o u r c e

C o n f i g u r a t i o n

O p t i o n

f S Y S / 4

L X T

L I R C

C o n f i g u r a t i o n O p t i o n

D i v i d e b y 2 1 2 ~ 2 1 5

f S

T i m e B a s e I n t e r r u p t

2 1 2 / f S ~ 2 1 5 / f S

Time Base Interrupt

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