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Original question:

[FAQ] TMS570LC4357: Step by step procedure to execute a function in internal RAM on TMS570LC4357

TMS570LC4357: RM44L520PZ

Martin Jean-Daniel
Intellectual 405 points
Part Number: TMS570LC4357
Other Parts Discussed in Thread: RM44L520

Hi,

I applied this ste-by-step tutorial to execute some parts of my code in the RAM area, with the purpose of getting a reduction of the time execution of real-time critical instructions.

I see in the datasheet SPNS229C figure 5.2 that no wait state is required for RAM access, whereas Flash access requires wait states. I deduce that a reduction of the time execution of critical code can be reach when executing it in RAM.

I checked in my tested MCU that the setup of the wait states is conform with the datasheet (all wait state setup with 0 except RWAIT = 2 because Fcpu=120MHz).  

I have checked that the code was really executed in RAM on my RM44L520PZ MCU running at 120MHz. I did not enable any RAM protection (MPU are all disabled).

I made time measurement of the critical code execution and I am disappointed to observe no reduction of the execution time.

Did someone made such execution time measurement and comparisons (code executed in flash and in RAM) ?

Best regards,

JDM

  • 0
    TI__Guru 69701 points

    Hi JDM,

    How you measured the timings?

    Can i get your code to debug and test it at my end?

    --

    Thanks & regards,
    Jagadish.

  • 0 in reply to jagadish gundavarapu
    Intellectual 405 points

    Ji Jagadish,

    I made further investigations and tests. It seems to be normal with this reference that with a low RWAIT value (for Flash wait states), the execution time and RAM or in Flash are similar. 

    the following datasheet extraction of the TMS320F2879D requires same amount of wait states as a function of the frequency to the RM44L520 reference :

    It also indicates that "Flash performance for sequential code is equal to execution from RAM".

    Here is some measurement results on RM44L520PZ device: 

    Code execution location

    Critical task execution duration (µs)

    In Flash with RWAIT=  0

    44,1

    In Flash with RWAIT=  1

    44.1

    In Flash with RWAIT=  2

    45,1

    In Flash with RWAIT=  3

    46.4

    In Flash with RWAIT=  4

    48,1

    In Flash with RWAIT=  5

    50.6

    In RAM

    44.1

    To conclude, with low flash wait states, code execution time in Flash and RAM are similar.

    Best regards,

    JDM