PIC18F252 software program

[Vovachess]

I have one nice problem with my software on PIC18F252.
In the software I have parameters defined in ram:

unsigned char inbuffer[60];/*input/output buffer*/
unsigned char Mode_Power1=2;/*Working state of server1*/
unsigned char Mode_Power2=1;/*Working state of server2*/
unsigned char supcyc=0;
unsigned char cyctime=20;
unsigned char init_webparamerets_count=0;

The Software works correctly over 20-24 hours. And once some parameters will be changed by controller! I can control data traffic between controller and PC on RS232. I see that controller makes once:

Mode_Power1=38;
Mode_Power2=13;

What could it be, that controller changes parametes values during execution? My software can not set so strage values! The most strage thing, that the software works hours correctly and suddenly changes!
Could it be stack overfull? Compile problem�.Something else?

Thanks for ideas.

[Ttelmah]

The 'most likely' cause is that 'inbuffer' is overflowing somewhere. This would then corrupt the values immediately latter in the memory, and since the compiler will normally store variables 'as they are declared', this really is the highest probability. You need to look at the .sym file, and find where the variables are actually declared in memory, and then look at the code that accesses the thing immediately 'in front' of this (probably inbuffer'). Remember that a 60 element array can only hold values from 0-59.
The second most likely cause, is a power spike. RAM is about the most sensitive thing to variations in the supply.
The stack, has no relation/connection to the main RAM, but a stack overflow (if you don't trap this - on most processors you can force a restart if this occurs), can lead to the processor jumping anywhere in memory, and 'unexpected' results. The .LST file, shows how close to the stack limits your code goes.

Best Wishes

[ckielstra]

Sounds like a buffer overflow problem. This happens for example when you write to an array using an index larger than the array size, the variables in memory directly following the array will be corrupted.

Buffer overflows are often difficult to debug because they only happen once in a while, often after running successfully for several hours, days or even years. Therefor don't try to find the cause of the error by testing, but try finding it by studying your source code.

You already have a strong clue by noticing that two of your variables changed values. Have a look at the symbol file for your project (*.sym). It will look something like

[Vovachess]

Hello
Thank you very much for your answers! It looks like really this problem.
I ll check it. It is really strong error......!!!!
Thanks you