Auto-recovery techniques

AN1015

14/19

DocID5833 Rev 2

This is a poor approach, a far better method is to use the watchdog timer register to check

the execution times of individual software routines and in case of an abnormality to react

promptly before the watchdog end of count and either perform an immediate reset or go into

a software recovery routine.

Figure 4. Local control by the watchdog

3.3

Using the reset flags to identify the reset source

There are several possible internal reset sources: LVD (Low Voltage detector) or Watchdog

reset, POR (Power On Reset), hot reset (parasitic or external reset following a low state of

the Reset pin).

The reset source is flagged in a “reset register” and this information is kept as long as the

MCU's power supply is on.

Figure 5 shows how you can test the reset register at the beginning of your program and

then branch to a context recovery routine (depending to the detected reset source) instead

of restarting the "Power On Reset" initialization routine which is often complex and time

consuming.

It is very important to detect and manage parasitic resets as they are the most usual cause

of microcontroller EMC failures.