CCS/TMS320F28035: Clock cycles

Indrajit Lawande95

Part Number: TMS320F28035
Other Parts Discussed in Thread: CONTROLSUITE

Tool/software: Code Composer Studio

Hi, I am using TMS320F28035 . I have written a very basic simple code for boost converter . within ISR i am reading ADC readings and multiplying result with some scaling factor and after that standard formula for boost converter . When i measured clock cycle for ISR it taking 965 clock cycle , but here within this ISR just 2 -multiplications , 1 division , and 3/4 - data transfer . So my question is why it taking so many clock cycles . As per data-sheet of controller it is given that it this controller can do 32x32 multiplication within single clock cycle .

How can I reduce clock cycles??

Thanks and Regards,

Indrajit.

over 8 years ago

0 Richard Poley over 8 years ago

TI__Mastermind 27200 points

Indrajit,

You are using a fixed-point controller, so the single cycle 32x32 multiplication applies to fixed point data. Those scaling constants will be seen as floating-point numbers by the compiler because neither can be represented as integers. Both the multiplications, and probably the division, will be making calls to the RTS library to support floating point format and this is what's consuming all those cycles.

The best way to manipulate floating point like data on a fixed point C28x is to use the IQ math library. I recommend you open up the IQmath documentation and examples in controlSUITE. You'll find the cycle count will go down a lot.

Regards,

Richard

0 Indrajit Lawande95 over 8 years ago in reply to Richard Poley

Expert 1350 points

Thanks for your suggestion .
I will try to write the ISR part using IQmath .

Thanks.

0 Indrajit Lawande95 over 8 years ago in reply to Indrajit Lawande95

Expert 1350 points

Hi, with IQmath it taking only 78 clock cycles ...
thanks again .

0 Indrajit Lawande95 over 8 years ago in reply to Indrajit Lawande95

Expert 1350 points

Hi , But when I changed the linker command file from RAM to flash to run from flash .it is taking 640 cycles instead of 78 cycles when same code was running from RAM . Why ? and how can i reduce this count further.
Thanks .

0 Richard Poley over 8 years ago in reply to Indrajit Lawande95

TI__Mastermind 27200 points

Indrajit,

There could be several reasons, but when you move from RAM to flash you'll need to do more than just change the linker command file. The flash array must be configured properly to get the best performance, and the functions which do this must be run from RAM.

In the peripheral header file examples for F28035 in controlSUITE you can find a project called "flash_f28035" which shows how to do this. I recomend opening that project and reviewing the code. In the main program, lines 179 - 188 load the time critical functions into RAM before calling the InitFlash(); function.

There is also an application note with example code which may help you, here:
http://www.ti.com/lit/an/spra958l/spra958l.pdf

Regards,

Richard

0 Indrajit Lawande95 over 8 years ago in reply to Richard Poley

Expert 1350 points

I will go through same .. I understood the reason . Thanks.

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CCS/TMS320F28035: Clock cycles