Problem about the 32bit integer multiply operation in 28335!

Hex

Prodigy 10 points

Hi,

I defined a 32bit unsigned integer varible, such as "Uint32 temp".

In ccs3.3, I examined the result of integer multiply operation.

The code is "temp = 320 * 240". The real value of this multiplication

is 76800(excess 16bit interger range). But the value of "temp" in watch

window is 11264. The value between bit31~bit16 is discarded. Why?

Thanks for your answer!

over 16 years ago

0 Vasily15156 over 16 years ago

Intellectual 295 points

Compiler treat 320 and 240 as a 16bit int, because standart type is int(it is 16bit len for C2000). Please, notice that Uint32 is unsigned long. So, You can do it like: temp = 320UL * 240UL; or temp = (Uint32)320 * (Uint32)240; or const Uint32 a = 320; const Uint32 b = 320; temp = a * b; //here compiler know about a and b is 32bit len

0 Mitja Nemec over 16 years ago in reply to Vasily15156

Genius 5885 points

Hi Vasily, Hex,

Just a note: This is a standard (and proper) C compiler behavior it is not specific to the TI C2000 compiler

Regards, Mitja

0 Vasily15156 over 16 years ago in reply to Mitja Nemec

Intellectual 295 points

Yes, ofcourse. here I mean C2000 specific is 16bit standart type(int). In Microsoft Visual C (32bit comiler) standart type is 32bit len and Hex's code will work fine by default.

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Problem about the 32bit integer multiply operation in 28335!