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TMS320F2800137: Capacitance selection of F2800137's XRSn pin

feng
Prodigy 200 points

Part Number: TMS320F2800137
Other Parts Discussed in Thread: C2000WARE, , SYSCONFIG

Hi, TI's expert

  I've got a issue about F2800137. Here is the Description.

  From the hardware design guide/ spec,  F2800137 need a 2.2K - 10K pull-up resistor from VDD to XRSn pin, and for noise decouple, a cap smaller than 100nf can be placed on this pin. And I did on that way.

  But I found that, the code can just run in debug mode, which means code run in RAM. Once change into Release Mode, which means I downlaod the code to flash, the DSP would not RUN at all.

  After debug, I position the issue with, the sequence of XRSn and GPIO24/ GPIO32. The XRSn is valid about 1.2ms than GPIO32.

  When I add a 1uf cap on XRSn pin, it can add RC time to meet POR sequence. DSP can load code from flash. But the F2800137 spec says that XRSn pin capacitance can not bigger than 100nf

  So, I wanna ask if I can adjust the capacitance? Or other way to slove this.

  Thans

  • 0
    TI__Mastermind 23821 points

    Hi Feng,

    Are you able to observer this behavior across multiple devices or is this isolated to only a single device? The 100nF suggestion is to pertinent to the watchdog function which you may not be testing. It is to ensure the XRSn is driving low within 512 clock cycles of the watchdog reset, any higher capacitance could delay the reset and pose an issue to device in rare cases depending on device conditions. 

    Do you mean you are in the boot from flash boot mode, as there are a few other boot modes which you want to ensure you are using the correct one

    Is there any external supervisory circuit being used to drive the XRSn pin?

    Regards,

    Peter

  • 0 in reply to Peter Luong
    Prodigy 200 points

    I find that the root case of the issue is, the sequence of GPIO24/ GPIO32 and XRSn. Now I've fixed that.

    by the way, I find that the ccs20.3 can not built the cputimer.h/ can.h and other head files, and that is because the  __TMS320C28XX__ are not defined, how can I do to fix this, please give me a method or link to solve this.

  • 0 in reply to feng
    TI__Mastermind 23821 points

    Hi Feng, 

    Thank you for your patience as the US has had Thanksgiving holiday all of last week. 

    Regarding the CCS issue, this should be defined in the device.h, are you using the provided device.h from the SDK? You may also try and test adding __TMS320C28XX__ to the predefined symbols in the Project Properties

    Regards,

    Peter

  • 0 in reply to Peter Luong
    TI__Mastermind 23821 points

    But again this should also be defined by CCS and I haven't seen issue with it. Can you make sure the latest C28x compiler is being used in CCS and the device is defined as F2800137 or Generic C28x Device

  • 0 in reply to Peter Luong
    Prodigy 200 points

    Thanks for reply.

    The cfg files are generated by sysconfig tool, and the project is devploped by C:\ti\C2000Ware_6_00_01_00\driverlib\f280013x\examples\empty_projects, and I delete the TMS320F2800137_LaunchPad.ccxml file because I made my self board.

    if I need to add the __TMS320C28XX__ to the predefined symbols in the Project Properties, is there a guide or link that I can take a look.

    Thanks.

  • +1 in reply to feng
    TI__Mastermind 23821 points

    Hi Feng,

    You can refer to here: https://software-dl.ti.com/ccs/esd/documents/ccs_variables_in_source_code.html This is for older CCS but the properties setup should be the same when you right click the project

    Regards,

    Peter

  • 0 in reply to Peter Luong
    Prodigy 200 points

    Thanks for reply.

    And my issue is solved.