AN3181

Class B software package

Doc ID 17286 Rev 2

11/31

3

Class B software package

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

workspace organization under different tools is described together with its configuration and

debugging capabilities.

3.1

Basic software principles

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

firmware library are described in detail at this section.

3.1.1

Fail Safe mode

FailSafe() routine is called (defined in stm8x_stl_startup.c file) at any fail detection. The

program stays in a never ending loop waiting for WDG reset. Except for some debugging

features, the routine is almost empty. When editing this routine, the user must remember to

include procedures necessary to keep the application in a safe state.

If the user wants to recognize the error raised, the debug or verbose mode described in

Section 3.3: Package configuring and debugging can be used. In debug mode the

independent WDG is refreshed inside the never ending loop to prevent resetting the

microcontroller when a failure occurs.

3.1.2

Class B variables

Class B variables are dedicated variables defined by the user as critical to the application.

They are always stored as a pair of complementary values in two separate RAM areas. Both

normal and redundant values are always placed into non-adjacent memory locations. Partial

transparent RAM March C- or March X test is performed permanently on these two regions

through the system interrupt routines in run mode. The integrity of the pair is compared

before the value is used. If any value stored is corrupted, FailSafe() routine is called. An

example of RAM configuration is shown in Figure 1. The user can adapt the RAM space

allocation according to application needs and with respect to device hardware capability.

Figure 1.

Example of RAM memory configuration for STM8S20x