The variable is defined in *.h:
static unsigned char cPwLe[3] = {0};
cPwLe[cCh] = Power_Level(cP[cCh]); //Here value is right
cPower = cPwLe[cCh]; //Here value is always 0
The variable is defined in *.h: static unsigned char cPwLe[3] = {0}; That "static" is an error. This keyword should quite exactly never appear in a header file. Please refer back to your C textbook to understand what it does, and why that's not what you want to do, here. Furthermore, you should never define a variable in a header file, either. It may only be declared there. If the distinction between these two terms isn't clear to you, stop what you're doing right now, and get back to that C textbook.
If the distinction between these two terms isn't clear to you, stop what you're doing right now, and get back to that C textbook. Hans-Bernhard, Are you actually suggesting that one need to know what one is doing? You are totally out of step with the times and must be very old. This is totally out of fashion these days.
If the reason you have a global variable is that some routine other than the interrupt handler uses the value, then you need to declare the global volatile (as well as extern). If only the interrupt handler uses the global variable -- that is, the variable is global only so that it preserves state between interrupts -- then you should probably remove the reference from the header file and declare the variable static so that no other routine can access the variable. You also might consider making the variable a static local, declared inside the interrupt handler.
Can you tell why? Just a MOD caculating result in the mistake:
if (cC%(cPower+1)==0) ...
if (cC%(cSV+1)==0) ...
Can you tell why? No. Nor can anybody else, from what you wrote. You're not giving anywhere nearly enough information for that. Just a MOD caculating result in the mistake: In what mistake? When be corrected to if (){} and add statement There's nothing to be corrected about what you wrote --- ripped completely out of context as it is, it's impossible for anyone not sitting on your chair to find out what "correct" might possibly mean, for this snippet of code.
Study the meaning and use of the volatile keyword. Code generated for the main routine might not use the latest value of a variable updated by an ISR unless that variable is declared volatile.
It's called a global variable because it's recognized almost everywhere, just like your American express card. The danger is modifying it in an isr and using it several places in main loop code assuming it is doesn't get modified between reads. It usually leads to much hair-pulling and cursing.
using it several places in main loop code assuming it is doesn't get modified between reads that is not the most common reason for "much hair-pulling and cursing". The one most get caught on is reading an int/short/long (anything beyond 8 bits) in main without disabling interrupt. Erik