4/10

ST7 CHECKSUM SELFCHECKING CAPABILITY

2 USING THE SAME ROUTINE WIHT A USER’S APPLICATION

2.1 FLASH

To use the safe routine, do the following:

s

Add the “Safe” routine to the application.

s

Select the “define” statement corresponding to the MCU device used in the application.

s

Change the ‘vectit’ segment depending on the device chosen.

s

Modify the reset vector to point to the Safe routine and not to the main one.

s

Include the right .inc mapping file at the beginning of the application.

s

Update the .bat file for the compilation.

s

Generate the .s19 file.

s

Use the emulator or the Development Kit with STVD7: first fill the emulator memory with $83

(for example): before opening the application workspace, go into Debug mode (without any

opened workspace), right-click on the Memory Window and select Fill Memory:

Fill the memory with 0x83 in 2 steps (because there are 2 sectors): first from 0xE000 to

0xEFFF, then from 0xF000 to 0xFFFF. You then just have to open your workspace and your

program will be written into the Flash area that has bee initialized with $83.

To calculate your application checksum:

s

Run the program the first time with the emulator in order to get the checksum: put a

breakpoint on the line after the “end1” label (see safe.asm in the zip file with this application

note).

s

Fill the CS0, CS1, CS2 variables (in constant.asm) with the obtained checksum value stored

in ch_sum (ch_sum, {ch_sum+1}, {ch_sum+2}).