delay function in winavr

[ashish.master2]

i am learning atmega 8 microcontroller.
i am having a problem in using the delay function
i have seen some programs
some define # define F_CPU 1000000Ul
i want to ask which clock frequency they define, external clock or internal clock.
also what if i do not define it in my program, which clock will it be using internal clock or external clock.

 

[nandhu015]

Define F_CPU is used to define the clock frequency which you are using in your hardware. You may use either internal or external frequency.

If you dont define it will create error.

Nandhu

 

[ashish.master2]

i am not using it, it is not showing any error, that why i was asking if we dont define it, which frequency it means

 

[Kurenai_ryu]

maybe it's defined at the makefile... (at winavr you have a makefile generator which comes with a 8MHz F_CPU defined value)... but I think it's not used in very simple programs... just when you add the #include <utils/delay.h> or maybe the baudrate calculator... If you don't use any of them... I think the program doesn't take in account the F_CPU constant (but i'm not sure... for me, it's always defined at the makefile)

Also! if you are plannig to make a huge program with many C files... it's better to have just one F_CPU define... again.. at the makefile... so it doesn't mess with multiple F_CPU values at individual files...