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TMS320F28335: Flash Wait State Time

stevenh
Guru 19965 points
Other Parts Discussed in Thread: TMS320F28335, TMS320F28374S

Hello,

The TMS320F28335 datasheet specifies a 37ns flash read access time.  What does the read access time depend on? Can it vary greatly between parts?  

I noticed one of the newest TMS320 devices (i.e.TMS320F28374S)  specifies 2 wait states for 150Mhz.  That's a lot faster than the TMS320F28335, which is greater than 5 wait states.  Is the newer device using a better flash module?

Stephen

  • 0
    TI__Guru** 112395 points

    Hi Stephen,

    Flash access time depends on technology. Devices you are comparing, are build on different flash technology. TMS320F28335 device is on F05 technology where as TMS320F28374S is on F021, which is much faster.

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    Guru 19965 points

    Thanks Vivek,

    Does TI have any papers that compare/discuss the two?  Does the TMS320F28374S have a flash pipeline?   Also, will the TMS320F28335 be getting the new Flash technology in the near future?

  • 0 in reply to stevenh
    TI__Guru** 112395 points

    Hi Stevenh,

    Does TI have any papers that compare/discuss the two?

    TRM of both the device should provide required information on this. If you need some specific info which is not available in TRM, please let us know and we'll try to provide it. 

      

    Does the TMS320F28374S have a flash pipeline?

    Yes, it has a pipeline.

    Also, will the TMS320F28335 be getting the new Flash technology in the near future?

    TMS320F28374S device should have all the feature like TMS320F28335. Please have a look at this device Data Sheet/TRM.

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    Guru 19965 points

    TMS320F28374S device should have all the feature like TMS320F28335. Please have a look at this device Data Sheet/TRM.

    I was mainly referring to the speed of the devices.  The TMS320F28335's flash access time seems to be 1/2 times slower (>37ns which is  >5 or more wait states, see page 182 ) as compared to the TMS320F28374S (<= 3wait states, see page 45). 

    Is the 37ns access time measured at a 150Mhz clock frequency?

  • 0 in reply to stevenh
    Guru 19965 points

    Hello Vivek,

    You have answered all my questions except the following:
    1. Is the 37ns access time measured at a 150Mhz clock frequency.  What would make it greater than 37ns, i.e. processor speed and etc?

    2. Does TI have any intention of incorporating the faster flash technology into the TMS320F28335?

    Stephen

  • 0 in reply to stevenh
    TI__Guru** 112395 points

    Hi Stephen,

    1. Is the 37ns access time measured at a 150Mhz clock frequency.  What would make it greater than 37ns, i.e. processor speed and etc?

    As I mentioned earlier, access time depends on technology not on processor speed. Based on the processor speed, user need to set the proper wait state to match it with access time. E.g. if the access time is 37ns and processor speed is 100MHz (10ns cycle) then user need to set the wait state as 4 and if the processor speed is 50MHz (20ns cycle) then wait state need to be set as 2. 

    2. Does TI have any intention of incorporating the faster flash technology into the TMS320F28335?

    At present we don't have any such plan. As I mentioned earlier,  TMS320F28374S device offers all the features as TMS320F28335 with improved flash performance and additional MIPS. 

    Regards,

    Vivek Singh