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C6747 - EMIF asynchronous timings

Nir Gabrieli
Prodigy 20 points

I'm using the EMIFA in asynchronous mode,

I want to config the CEnCFG registers for a flash device.

According to the EMIFA user guide in order to calculate the SETUP,STROBE and HOLD timings i need several absolute timing values from the FLASH and the DSP.

I extracted the FLASH values from it's datashhet.

But i can't seem to understand the loaction to extract the DSP vaues - i need to extract three values - td.tsu and th.

in the C6747 datasheet in section 6.11 i find two sets of values - one for the SDRAM and one for the asynchronous mode.

in the asynchronous mode set - there is no td value (only tsu and th).

where do i find the td,tsu and th values ?

 

p.s.

I don't understand why in the EMIFA example the values are referred to the EMA clock - which is not in use when using asynchronous  mode.

thank you very much.

 

 

  • 0
    TI__Mastermind 27585 points

    Hi Nir,

    A wiki page has just been created and contains a spreadsheet which will calculate the CEnCFG register for you. You can find the link here.

    It looks like the information in the appendix of the EMIFA user guide is incorrect. Instead you should look at the TMSDM6446 EMIFA User Guide, section 3.2.2. The calculation spreadsheet uses the formulas from that document, so please use that while the OMAP-L1x document is updated. For these formulas, 'td' is not required.

    Jeff

     

  • 0 in reply to jc-ti
    Prodigy 20 points

    Jeff,

    thank you very much for the quick response.

    but unfortunately  both the user guide and the spreadsheet you recommended are referring to a NAND flash, while i use a NOR flash.

    so the values are differnet by name and function, besides that i still don't know where do i find the C6747 EMIFA tsu and th...

    thank you.

  • 0 in reply to Nir Gabrieli
    TI__Guru* 84110 points

    Nir Gabrieli,

    Although I am not familiar with the spreadsheet that Jeff has recommended, the timing parameters may be very similar and the spreadsheet may have the formulas that you need to use.

    In the DM6446 EMIF User's Guider, you can follow the description for Interfacing to Asynchronous SRAM for your situation of using a NOR Flash device. The parameters will be the same even though their values or delays will be different.

    In the C6747 datasheet, the EMIFA Asynchronous Memory Switching Characteristics table has the parameters that you are looking for. Timing is provided relative to the control signals such as EMA_WE and EMA_CE, so there is a delay from EMA_D valid to EMA_WE low and from EMA_WE high to EMA_D invalid.

    The use of EMA_CLK is because the time that you add to the minimum delays is measured in increments of EMA_CLK. If you increase WSTROBE by 1 then you will actually add one clock period of EMA_CLK to the write strobe time. You are correct that EMA_CLK is not used for latching data, but the sequencing of the control and data lines is measured in steps of EMA_CLK clock periods.

    Regards,
    RandyP

     

    If you need more help, please reply back. If this answers the question, please click  Verify Answer  , below.