SAF-C504 datasheet(38/71 Pages) INFINEON

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C504

Data Sheet

2000-05

Oscillator Watchdog

The Oscillator Watchdog of the C504 serves for three functions:

– Monitoring of the on-chip oscillator’s function

The watchdog supervises the on-chip oscillator's frequency; if it is lower than the

frequency of an auxiliary RC oscillator, the internal clock is supplied by this RC

oscillator and the C504 is brought into reset. If the failure condition disappears, the

C504 executes a final reset phase of typically 1 ms in order to allow the oscillator

to stabilize; then, the Oscillator Watchdog reset is released and the part starts

program execution again.

– Fast internal reset after power-on

The oscillator watchdog unit provides a clock supply for the reset before the on-chip

oscillator has started. The Oscillator Watchdog unit also works identically to the

monitoring function.

– Control of external wake-up from software power-down mode

When the software power-down mode is terminated by a low level at pin P3.2/INT0,

the Oscillator Watchdog unit ensures that the microcontroller resumes operation

(execution of the power-down wake-up interrupt) with the nominal clock rate. In the

power-down mode, the RC oscillator and the on-chip oscillator are stopped. Both

oscillators are started again when power-down mode is released. When the on-chip

oscillator has a higher frequency than the RC oscillator, the microcontroller starts

operation after a final delay of typically 1 ms in order to allow the on-chip oscillator

to stabilize.

SAF-C504 数据表(PDF) 38 Page - Infineon Technologies AG