STFPC311 View Datasheet(PDF) - STMicroelectronics

Part Name

Description

MFG CO.

STFPC311

Front panel controller/driver with standby power management

STMicroelectronics 

3 Initialization

STFPC311

3.4 Standby or power-down mode

Once the STFPC311 detects the status change of the READY to a logic low or after the preset

waiting time (1s to 15s) has elapsed, the STFPC311 sets the STBY pin to a logic high to turn off

the power. The MUTE signal is set to high before the power is turned off. The STFPC311

always senses the level on the READY pin during normal operation.

3.5 IR Decoding

Encoded IR data from photodiode is supplied to the IR_DATA_IN input pin. The data is

decoded by the internal remote control decoder module of STFPC311. In standby mode, the

remote control decoder recognizes a set of predefined commands (such as STANDBY, PLAY,

and OPEN/CLOSE), and takes appropriate action to manage the power supply.

These predefined commands are known as "hot keys" and are programmable. The decoded IR

commands are passed on to the main processor through the SPI interface by sending 3 bytes

of data on the DOUT pin.

3.6

Note:

Watchdog timer

The watchdog timer is used to detect an out-of-control microprocessor. The watch dog timer is

implemented in the STFPC311 to detect the abnormal processor behavior or processor-hung

condition. The default state of the watchdog timer is 10s when the device powers-up. It is

initialized by writing to the watchdog register and can be programmed to up to 15s (4-bit

watchdog timer, present in the configuration mode setting command).

If the processor does not reset the timer within the specified period, the STFPC311 will put the

entire system into standby mode to reset the appliance that has stopped abnormally. The action

to take when the watchdog timer has reached its count is to set the Watchdog Action register.

The watchdog timer can be reset by the host processor by sending a command to reset the

watchdog timer. The time-out period then starts over again. If the processor needs to be reset

as a result of a hung condition (signalled using the STBY output of the STFPC311), the

watchdog timer uses the amount of the time-out programmed into the Watchdog Register by

the user to generate an interrupt.

The accuracy of the timer is within ±10% the selected resolution. This depends on the value of

the external bias resistor, as it determines the internal clock frequency.

The watchdog function is automatically set to 10s upon power-up and the Watchdog Interrupt is

cleared. This boot-up watchdog timer is used to make sure that if the host processor hangs

during the first boot-up, the STFPC311 will put the system to standby mode. During the first

boot-up, the watchdog timer is disabled after the first READY signal is received.

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