AN3307 datasheet(14/37 Pages) STMICROELECTRONICS

14 / 37 page

Class B software package

AN3307

14/37

Doc ID 18186 Rev 4

Class B software package

This section highlights the basic common principles used in the ST software solution. The

workspace organization is described as well as configuration and debugging capabilities.

Any differences between the two supported development environments (IAR’s EWARM and

Keil’s MDK-ARM) are highlighted.

4.1

Basic software principles used

The basic software methods and common principles used for all the tests included in the ST

solution are described in detail in this section.

4.1.1

Fail Safe mode

If any failure is detected, the FailSafePOR() routine is called (defined in

stm32fxxx_STLstartup.c file). The program stays in an endless loop waiting for a

watchdog reset. Apart from some debugging features the routine is almost empty. Users

have to provide the content to the routine and ensure that it executes the right actions to

keep the application in a safe state.

The debug or verbose mode described in Section 4.3: Package configuration and

debugging can be used to identify which error has occurred.

4.1.2

Class B variables

Each class B variable is stored as a pair of two complementary values in two separate RAM

regions. Both normal and redundant complementary values are always placed in non

adjacent memory locations. A partial transparent RAM March C- or March X test is

performed continuously on these RAM areas by means of an interrupt subroutine. The pair

is compared for integrity each time before the value is used. If any value stored in the pair is

corrupted, Fail Safe mode is invoked. An example of RAM configuration can be seen in

Figure 1. Users can adapt the RAM space allocation according to the application needs and

the hardware capabilities of the device.

AN3307 Datasheet(PDF) 14 Page - STMicroelectronics