STV3550B STMicroelectronics, STV3550B Datasheet - Page 92

• Manufacturer Part Number: STV3550B
• Manufacturer: STMicroelectronics

Specifications of STV3550B

• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / Rohs Status: Compliant

TV chassis control
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Watchdog timer (WDT)
If a new edge is detected and if both registers (IRP0 and IRP1) are not empty, the new edge
cannot be taken into account until both registers are reset (the interval is not measured).
An internal algorithm is used to reset the flags and register values.
The IR input signal is preprocessed by a spike filter that determines whether all pulses
narrower than either 2 µs or 160 µs are filtered out before the signal is applied to the edge
detector.
Figure 59. Infrared receiver diagram
The WDT provides a fail-safe mechanism used to reset the chip if the software fails to clear
a counter within a given period.
The WDT has a counter which is clocked to provide up to a 2-second delay (11 bits). This
counter is periodically cleared by software as described below. If the software fails to clear
the counter within the timeout period, a “watchdog reset” signal is generated to reset the
chip. The counter is in the CLK_RTC clock domain.
A timeout register is used to configure the watchdog delay. The transfer occurs at the next
clear of the timer.
A status flag is set by a watchdog reset. This can be used to indicate to application code that
the system was reset by the watchdog timer. This status bit is reset only by the external
reset input to the chip.
The watchdog timer function is enabled by a control bit. If this bit is reset, a watchdog reset
must never occur.
The watchdog counter can be also stopped by an internal signal. When this signal is high,
the watchdog counter is stopped. This signal may be use by an emulator or a dedicated
mode to stop the watchdog activity.
64.133 kHz Clock
12-bit Counter
Register IRP0
Register IRP1
Error Flag
Control
Interrupt
STV3550
IR Input