This application note explains the different ways to reset the ST7 Microcontroller, including external reset, internal low voltage detect (LVD) reset, and internal watchdog reset. By selecting different reset sources, the application can be designed more effectively. The document also provides detailed information on the working principle and configuration options of the internal LVD reset.
The document details three primary sources for resetting the ST7 microcontroller: External Reset, Internal Low Voltage Detect (LVD) Reset, and Internal Watchdog Reset. It describes how these mechanisms act on the RESET pin and their specific behaviors during power-up and power-down sequences.
Furthermore, the note provides implementation schemes for external reset circuits. It covers simple RC delay circuits suitable for monotonous supply waveforms and transistor-based circuits using potential dividers or Zener diodes for unspecified or slow rise times. Recommendations are also given to ensure safe operation and avoid unwanted states during reset.
| Reset service routine vector address | FFFEh-FFFFh |
|---|---|
| Watchdog timeout period (ST7FLite0) | 2msec (@8MHz Fcpy) |
| Recommended pull-down resistor value (External Reset) | 10K or lower |
The various reset sources are External Reset, Internal Low Voltage Detect (LVD) Reset, and Internal Watchdog Reset.
It generates a reset when the supply voltage (Vpp) is below specific thresholds depending on whether the voltage is rising or falling.
A transistor-based circuit using a potential divider or Zener diode to bias the transistor is necessary if the supply voltage rise time is unspecified or very slow.