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Stellaris® ARM® LM3S Microcontrollers Forum
question on Rom function
instead of using SysCtlClockSet(...)...what is the advantage of using ROM_SysCtlClockSet(...)...or for that matter..what is the use of ROM functions in general?
The advantage is that you can save memory in flash by using the ROM functions.
can you elaborate a bit please????thank you.
The ROM versions of the functions reside in the ROM on your device. The non-ROM versions are linked in to your project, and so the functions are taking up flash space and making your code larger if you call them.
If the function you are calling is small, and you are calling it several times, you may be better off not using the ROM function. There's additional overhead to call the ROM version of the function, both in time and code size. Additionally, if you need fixes that were made to the function after the ROM was committed, you have to call the non-ROM version of the function to get those fixes.
However, since ROM is faster than Flash, why would it take longer to execute?
In any case, is it safe to say that if memory will not be an issue, that it is better to use the standard non-ROM functions?
The ROM is not faster than flash. Code executes out of either at the same speed.
It takes longer to call a ROM function because there's a little bit of extra code to call the ROM function that's not needed when calling a library function that's linked with your project.
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