STFPC320 STMicroelectronics, STFPC320 Datasheet - Page 14

• Manufacturer Part Number: STFPC320
• Description: Front Panel Controller/driver With Standby Power Management And Real-time Clock
• Manufacturer: STMicroelectronics

Functional description
4.5
4.6
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Interrupts/events handling by STFPC320
The STFPC320 interrupts the Host by pulling the IRQ_N/SQW pin to a low-level both in
normal mode of operation and during wake-up. The interrupt is enabled by STFPC320 when
any of the conditions occur:
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The IRQ_N/SQW is an active low level signal and is cleared only after the Interrupt buffer is
read. After reading the interrupt buffer, the Host will know the actual source of the interrupt.
This allows the Host to exactly know the event which caused the interrupt (e.g STBY key on
the Front Panel). The interrupt signal is used to inform the Host of any events detected by
the STFPC320. Note that the IRQ_N/SQW pin is an open-drain pin which requires an
external pull-up resistor.
Ready pin
The STFPC320 supports cutting-off power to the main board for standby operation for good
power management. STBY will be set to high when the READY transitions from high to low.
During a cold boot up or wake up from standby, if the READY pin stays low, the STFPC320
will assert the STBY when the guard timer has finished counting down to 0.
When the READY drops to a low, MUTE goes high immediately and soon after (2µs) the
STBY is asserted.
In the normal mode of operation, when READY is a high, the STBY is asserted only when
the guard timer is enabled and has finished counting down to 0. This is meant to put the
system into stand-by as the READY pin was stuck at high and the guard timer register was
not cleared before it finished counting down to 0. It is advised to disable the guard timer
during normal operation.
Figure 7.
Front panel key press in normal operation or during system standby state
Remote control key press in normal operation or during system standby state
A low-to-high transition on the external pin, PIN_AV8
Real Time Clock triggers (Alarm, Watchdog timer, Oscillator Fail)
Interrupts/events handling
STFPC320