Application description

AN3265

6/19

Doc ID 17860 Rev 1

1.2

Application schematics

DISCOVERY.

For STM8S-DISCOVERY implementation details, refer to the board schematics provided in

the STM8S-DISCOVERY user manual (UM0817).

Button1 requires an RC debounce filter to avoid triggering several interrupts. It consists of a

capacitor C and PB0 internal pull-up resistor (about 45 K

for Button1 as the internal pull-up of PBO I/O pin is used.

Figure 1.

Application schematics

1.3

Application principle

Two external pushbuttons are used to simulate malfunctions while the LEDs monitor the

application progress.

Button1 can be used in two different ways depending on the application context:

1.

To demonstrate the WWDG capability for managing software failures such as

application freeze:

When pressing Button1, the application lengthens the delay between two WWDG

refresh operations until this delay becomes too long. The WWDG then triggers a reset.

2.

To trigger a software reset.

Button2 is used to demonstrate CSS and IWDG recovery capabilities in case of HSE clock

failure. Pressing Button2 connects an additional high value capacitor to the OSCIN pin