STLED325 datasheet(26/62 Pages) STMICROELECTRONICS

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Functional description

STLED325

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Doc ID 17576 Rev 1

3.12

Remote control decoder

The remote control (RC) decoder module decodes the signal coming from IR_IN pin. The IR

remote control protocols recognized by STLED325 are Philips-RC-5, RCMM, Thomson

RCA, R2000, NEC and R-STEP protocols. The selection of remote control protocol to use is

done by setting the RC protocols register. The command from the remote control is used to

wake-up from standby and resume normal operation. All RC keys can be programmed to act

like RC hotkeys. Upon receiving any one of the designated hotkeys, wake-up operation

begins.

The address of the appliance (8-bit) is stored first into the internal RAM. Then, the command

for the hotkeys is programmed into the internal RAM. Each hotkey memory address could

accommodate one byte (8-bit). Usually one byte is reserved for one command. The hot-keys

can be configured to wake-up the system by more than one RC device address (up to a

maximum of 8 device addresses).

3.13

Interrupt

The STLED325 interrupts the Host by pulling the IRQ_N pin to a low-level both in normal

mode of operation and during wake-up. The interrupt is enabled by STLED325 when any of

the conditions occur:

– Front panel key press in normal operation or during system standby state

– Remote control key press in normal operation or during system standby state

(including the toggle bit changes for all RC protocols)

– A low-to-high on the external pin, WAKE_UP

– Real time clock triggers (alarm, watchdog timer, 32 kHz oscillator fails)

– GPIO input changes

– Low battery indication

– Thermal shutdown

The IRQ_N 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

STLED325. Note that the IRQ_N pin is an open-drain pin which requires an external pull-up

resistor.

Figure 9.

Interrupt

The interrupt output is of active low level type.

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