AN421

Summary

Doc ID 2476 Rev 2

9/11

4

Summary

Protection of software against externally generated perturbations can be made by additional

test routines.

This protection can easily be increased by using the ST9 Timer/Watchdog bringing software

reliability and security. With the Timer/Watchdog the ST9 program can control that the

software executing properly. Additionally, when restarting the Timer Watchdog from values

(AAh, 55h) located at the bottom of the system stack two additional security functions are

added:

●

Test of the integrity of the Register File or the RAM space

●

Provision of a system reset in the case of stack overflow.