HT95R55 datasheet(39/80 Pages) HOLTEK

39 / 80 page

HT95R54/HT95R55

Rev. 1.00

March 3, 2010

Interrupt Priority

Interrupts, occurring in the interval between the rising

edges of two consecutive T2 pulses, will be serviced on

the latter of the two T2 pulses, if the corresponding inter-

rupts are enabled. In case of simultaneous requests, the

following table shows the priority that is applied. These

can be masked by resetting the EMI bit.

Interrupt Source

All Devices Priority

Reset

External Interrupt

Timer 0 Interrupt

Timer 1 Interrupt

Peripheral Interrupt

Real Time Clock Interrupt

Multi-function Interrupt

In cases where both external and internal interrupts are

enabled and where an external and internal interrupt oc-

curs simultaneously, the external interrupt will always

have priority and will therefore be serviced first. Suitable

masking of the individual interrupts using the INTC reg-

ister can prevent simultaneous occurrences.

External Interrupt

For an external interrupt to occur, the global interrupt en-

able bit, EMI, and external interrupt enable bit, EEI, must

first be set. An actual external interrupt will take place

when the external interrupt request flag, EIF, is set, a situ-

ation that will occur when a high to low transition appears

on the INT line. When the interrupt is enabled, the stack is

not full and a high to low transition appears on the exter-

nal interrupt pin, a subroutine call to the external interrupt

vector at location 04H, will take place. When the interrupt

is serviced, the external interrupt request flag, EIF, will be

automatically reset and the EMI bit will be automatically

cleared to disable other interrupts.

Timer/Event Counter Interrupt

For a Timer/Event Counter interrupt to occur, the global

interrupt enable bit, EMI, and the corresponding timer

interrupt enable bit, ET0I or ET1I, must first be set. An

actual Timer/Event Counter interrupt will take place

when the Timer/Event Counter request flag, T0F or T1F,

is set, a situation that will occur when the Timer/Event

Counter overflows. When the interrupt is enabled, the

stack is not full and a Timer/Event Counter overflow oc-

curs, a subroutine call to the timer interrupt vector at lo-

cation 08H or 0CH, will take place. When the interrupt is

serviced, the timer interrupt request flag, T0F or T1F, will

be automatically reset and the EMI bit will be automati-

cally cleared to disable other interrupts.

Peripheral Interrupt

For a Peripheral interrupt to occur, the global interrupt

enable bit, EMI, and the corresponding peripehral inter-

rupt enable bit, EPERI, must first be set. An actual Pe-

ripheral interrupt will take place when the Peripheral

interrupt request flag, PERF, is set. This will occur when

the DTMF receiver detects a valid character, a ring/line

reversal is detected, an FSK carrier detected, an FSK

data packet is ready or the FSK raw data exhibit a falling

edge. When the interrupt is enabled, the stack is not full

and a Peripheral interrupt request occurs, a subroutine

call to the peripheral interrupt vector at location 10H, will

take place. When the interrupt is serviced, the periph-

eral interrupt request flag, PERF, will be automatically

reset and the EMI bit will be automatically cleared to dis-

able other interrupts.

Real Time Clock Interrupt

For a Real Time Clock interrupt to occur, the global inter-

rupt enable bit, EMI, and the corresponding real timer

clock interrupt enable bit, ERTCI, must first be set. An

actual Real Time Clock interrupt will take place when the

Real Time Clock request flag, RTCF, is set, a situation

that will occur when the RTC times out which will occur

every second. When the interrupt is enabled, the stack

is not full and a Real Time Clock interrupt request oc-

curs, a subroutine call to the real time clock interrupt

vector at location 14H, will take place. When the inter-

rupt is serviced, the timer interrupt request flag, RTCF,

will be automatically reset and the EMI bit will be auto-

matically cleared to disable other interrupts.

Multi-function Interrupt

For a Multi-function interrupt to occur, the global inter-

rupt enable bit, EMI, and the corresponding multi-func-

tion interrupt enable bit, EMFI, must first be set. An

actual Multi-function interrupt will take place when the

Multi-function interrupt request flag, MFF, is set, a situa-

tion that will occur when PC0 or PC5 receive a falling

edge, PC7 receives a rising edge, an SPI/I

2C interrupt

occurs, an external peripheral has a falling edge or a

Timer2 overflow occurs. When the interrupt is enabled,

the stack is not full and a Multi-function interrupt request

occurs, a subroutine call to the multi-function interrupt

vector at location 18H, will take place. When the inter-

rupt is serviced, the multi-function interrupt request flag,

MFF, will be automatically reset and the EMI bit will be

automatically cleared to disable other interrupts.

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