Class B solution structure

AN3181

20/31

Doc ID 17286 Rev 2

The user actually has a choice of three different methods for calculating the CRC (see

Figure 8) over the code memory content in the project.

●

An 8-bit check sum calculation over the 16-bit address space can be used for checking

up to 64 Kbytes of memory code, the simplest method.

●

A 16-bit check sum calculation over the 16-bit address space can be used for checking

up to 64 Kbytes of the memory code; this method is more precise and is the default

method.

●

A 16-bit check sum calculation over all the possible address space can be used when

the code memory exceeds 64 Kbytes, 24-bit addressing must be used; this way uses

the most code space and is the most time consuming.

The STM8 firmware includes six separate source files defined for each of these methods.

There is one pair for each method: one used for startup and one for run time. The user

should include the correct source file pair into the project.

Figure 8.

FLASH startup self test structure

4.2.4

Full RAM March C-/X self test

The whole RAM space is alternately filled and checked simultaneously by zero and 0xFF

pattern in six loops, either by March C- or March X algorithms. March X algorithm is faster

as the two middle steps are skipped over. The first three loops are performed in incremental

order of addresses the last three in decremented order. In case of error, FailSafe() routine is

called.