Modulus calculation large numbers

Large numbers? Yes, probably in numbers larger than one byte.

I'm not sure I follow what you are saying here:
"a=0x496f6e77 and b = 0x3c"

Does the pointer a has the value 0x496f6e77, or does it point to an integer of such value?

You must make sure that the pointers a and b points to aligned data. Depending on what memory controller your chip has, you must also make sure that they point to readable memory :)

Byt why do you use pointers in the first place? The pointer is 32-bit - the same size as the integer values - so you will not gain any speed or code size to select pointers. All you do is to move the "read time" a number of clock cycles later since the actual memory access will happen inside the function instead of by being done by the caller.

Large numbers? Yes, probably in numbers larger than one byte.

I'm not sure I follow what you are saying here:
"a=0x496f6e77 and b = 0x3c"

Does the pointer a has the value 0x496f6e77, or does it point to an integer of such value?

You must make sure that the pointers a and b points to aligned data. Depending on what memory controller your chip has, you must also make sure that they point to readable memory :)

Byt why do you use pointers in the first place? The pointer is 32-bit - the same size as the integer values - so you will not gain any speed or code size to select pointers. All you do is to move the "read time" a number of clock cycles later since the actual memory access will happen inside the function instead of by being done by the caller.

Hi Thanks for the feedback

It was a bad pointer causing the fault, i did post reply seems to have gone missing :-)

Yes "a" points to an integer of such a value, seems to be ok now with these large numbers provided you ensure you are actually pointing at them :-{ my mistake.

ok about the pointer and int being the same size, new to ARM, been using 8 bit previously need to reset my mindset.

Thanks for the reply and hints though.
Darren