basic knowledge - processor
Guest
#3363992
hi
example:
if i start a main function with a var A = 0 and let it add one every
cycle:
main(){
int A = 0;
A++;
}
@ atmega 8 with 3.6mhz is 2.7 *10^-7 sec.
when there is no interrupt and i stop after eg. 10 cycles, is there
A=10??
First of all, unless A is declared volatile (http://en.wikipedia.org/wiki/Volatile_variable), the compiler will probably remove your code altogether, since it has no effect. Assuming you meant
you won't get one increment per cycle, because the increment and jump instruction together take more than one cycle.
Guest
#3364218
yeah thats exactly what i wanna know. does every command use one cycle?
Guest
#3364224
michael wrote: > does every command use one cycle? Hello Michael, you wanna look up the assembler listing of your code to find out what the compiler generated. After that you wanna look up the datasheet of the prcessor to find out how many (machine-) cycles each instruction requires, including the loop back. That gives you a exact numer of clock cycles required and therefore the exact time required for execution. rgds
Guest
#3364253
Hi Michael, to be sure, you have to disassemble your compiled code, cause there are many assembler instructions which needs more than one cycle e.g. RET needs 5 cycles (just take a look at the data sheet, Chapter "Instruction Summary"). Regards, René Reply |