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Original question:

TMS320F28388D: Unable to get Input clock source for the sample rate generator for McBSP A SPI clock module

TMS320F28388D: How to configure EMIF clock to low frequency ?

gurusha nahar
Expert 1260 points
Part Number: TMS320F28388D
Other Parts Discussed in Thread: ADS8365, C2000WARE

Hi,

I am using an external memory interface(EMIF) to interface the external ADC (ADS8365) using Asynchronous memory configuration.

I am reading the data to the EMIF memory region(EMIF1 CS2n - Program + Data 2M x 16 : 0x0010 0000 to 0x002F FFFF) by configuring the read strobe, hold and setup timing parameters.

I referred to the section: 12.6.2.2.1 Asynchronous 1 Configuration Register (ASYNC_CS2_CFG) Settings for EMIF to LH28F800BJE-PTTL90 Interface from TRM and accordingly set the corresponding read time according to the XADC timing characteristics.

One thing I am not sure about is how to read could be performed as both the modules have different operating frequencies, i:e; emif it is 200mhz and xadc is max. 5mhz.

Can we pull down the emif to lower frequency? As i am unable to read the data while configuring the peripheral properly.

Please note, we have not configured the strobe mode, and EM1DQM pin as well.

I have also attached the emif timing characteristic sheet to update the ASYNC_CS2_CR values.

 

EMIF Timing Calculation.docx

Kindly please check and revert asap.

Regards

Gurusha

  • 0
    TI__Guru** 115881 points

    Hi,

     One thing I am not sure about is how to read could be performed as both the modules have different operating frequencies, i:e; emif it is 200mhz and xadc is max. 5mhz.

    In ASYNC mode, you need to configure the SETUP/HOLD/STROBE value and according to the external device timing so clock frq should not matter. In fact clock is not needed for ASYNC mode.

    Are you thinking of driving the clock output as well ? If yes then we can not drive 5MHz clock output from EMIF.

    Regards,

    Vivek Singh

  • 0 in reply to Vivek Singh
    TI__Guru 62975 points

    Gurusha,

    Is there a reason for not using the F2838x's on-chip 16-b SAR ADC?

    You can use this EMIF configuration tool in C2000Ware to check your settings and timings:

    ~\C2000Ware_XXXX\boards\TIDesigns\F28379D_EMIF_DC\C2000-EMIF_ConfigurationTool.xlsx

    This EMIF appnote can provide some additional perspective on how things work.

    As Vivek mentioned, the asynchronous memory interface does not use a shared clock so only the setup and hold times need to be satisfied.

    -Tommy

  • 0 in reply to tlee
    Expert 1260 points

    Thanks tlee,

    tlee said:
    Is there a reason for not using the F2838x's on-chip 16-b SAR ADC

    We have an additional requirement.

    I am able to configure now!