STFPC320 datasheet(50/78 Pages) STMICROELECTRONICS

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Interrupt flags

STFPC320

50/78

Interrupt flags

The interrupt is sent on the IRQ_N/SQW pin when any one of the events occur: FP key

pressed, RC key pressed, PIN_AV8 transitions to a high or RTC events (watchdog timer,

alarm, oscillator fail). Simultaneously, the interrupt flags are set.

The micro-processor can read the interrupt flags by sending the “01100011” command.

After decoding this command, STFPC320 output one byte data as described below to

indicate the source of interrupt.

Figure 23.

Interrupt byte format

Note:

Default value of the register is 00h.

Description:

In the normal mode of operation (system is not in standby), the events described

below will cause any of the b4 to b7 bit to be set to 1 and IRQ_N/SQW will be

asserted low:

b4: RTC events

b5: PIN_AV8 transition to High

b6: valid remote control key detection

b7: front panel key detection

Having detected the assertion of IRQ_N/SQW pin, micro-processor should then read

the interrupt buffer to determine the external event causing the interrupt. Once read,

the buffer will be cleared and IRQ_N/SQW is released.

In the wake-up operation (system is in standby), the events described below will

cause any of the b0 to b3 bit to be set to 1 and wakeup occurs (STBY output is set to

low):

b0: RTC events

b1: PIN_AV8 transition to High

b2: valid remote control hotkeys detection

b3: front panel hotkeys detection

Once wakeup occurs, micro-processor should pull READY to high to indicate to

STFPC320 of a proper boot-up. The STFPC320 will then assert the interrupt to

indicate that an external event has been occurred. The microprocessor should then

read the interrupt buffer to determine the event causing the wakeup.

When the interrupt is caused by the RTC, the microprocessor should read the RTC

interrupt flag at address 0Fh to determine the specific RTC event: alarm, watchdog

timer of RTC or oscillator fail.

Preset-

value of

RTC or

Watchdog

or OFIE

PIN_AV8

RC hot

key

FP hot

key

Preset-

value of

RTC or

Watchdog

or OFIE

PIN_AV8

RCK

FPK

Preset-

value of

RTC or

Watchdog

or OFIE

PIN_AV8

RC hot

key

FP hot

key

Preset-

value of

RTC or

Watchdog

or OFIE

PIN_AV8

RCK

FPK

LSB

Normal operation

Wake-up operation

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