I have a noob question about F_CPU, because I don't really understand this stuff.
I have a project using AVRStudio 4. I set in the configuration the compiler option -DF_CPU=8000000UL.
I also put in my header file #define F_CPU 8000000UL
But it seems, this doesn't mean, that my controller is running on 8Mhz. Moreover it seems, that he is still running on the 1MHz internal clock.
1. Am I right?
2. Do I have to programm the fuse to set the clock to internal 8Mhz?
3. If so, for what is the compile option -DF_CPU if it has no influence on the real speed of the controller? Maybe the Answer is: Because than the compiler knows, how to put i.e. the delay into the ASM code. Is my assumption right? Are there other things I have to know for the -DF_CPU option?
Thanks in advance and regards