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Crystal Frequency setting limited to 20MHz

Christian Fuchs1
Expert 1260 points
Other Parts Discussed in Thread: TMS570LS3137, TMS570LS20216

Hello,

I want to use CCS v5.2 with a custom board with TMS570LS3137 and XDS100v2 emulator. I plan to use a 25MHz external oszilator connected to OSCIN pin. (This is within the specified range for this MCU)

Now I saw that the Crystal Frequency option in the Flash settings (see screenshot) is limited to 20MHz.

Will I get a problem with 25MHz?

Why is there a need to specify this frequency?

Thanks in advance

Christian

  • 0
    TI__Genius 9015 points

    Hello Christian,

    The 20MHz max crystal frequency is a holdover from the Hercules 130nm Flash process devices (TMS570LS20216/TMS470M) which had a max OSCIN frequency of 20MHz. This will need to be modified for our 65nm devices (TMS570LS31x/1227/04x/RM4x) and therefore will submit an issue into our tracking system for this.

    The reason this frequency needs to be specified is that the program and erase functions will setup the PLL to a specific system frequency to be used by these operations and therefore needs to know what frequency is being supplied on OSCIN.  The Flash controllers on the Hercules devices require scaling of the operation parameters based on the system frequency (HCLK) that the device is operating at.

    From a development perspective, you may not see any appreciable issues by supplying a 25MHz source while specifying 20MHz in CCS, but there is always the possibility of under programming or under erasing the device causing bit flip issues on subsequent reads of the device Flash.

  • 0 in reply to John Hall
    Expert 1260 points

    Hello John,

    in the meantime until this issue gets fixed, can I easely change this local in any config file of CCS?

    Or can you tell me when this issue will be fixed?

    Our first prototyp is almost ready for production and I don't want to change the oscilator part.

    Thank you

    BR

    Christian

  • 0 in reply to Christian Fuchs1
    TI__Mastermind 49120 points

    Christian,

    The OSCIN input frequency is limited from 5MHz to 20MHz, regardless of how the signal is generated. The datasheets will be updated to reflect this. The reason is that the flash banks and pump require minimum start-up times after a system reset (including power-up). There are counters inside the flash interface module that provide this minimum delay assuming a maximum default clock frequency of 20MHz. If the OSCIN is faster than 20MHz, these timings will be violated and could result in incorrect code execution.

    Regards,

    Sunil