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TMS320F28375D: EMxWE active low width in case of no EMxWAIT asserted in Extend Wait mode

ytakano
Genius 9095 points

Part Number: TMS320F28375D

Hi,

Our customer would like to know about tw(EMWEL) EMxWE active low width.
In a case of Extend Wait mode (ASYNC_CS2_CR[30](EW) = 1),
if EMxWAIT input signal is inactive, in other words, no "asserted",
what is a value of EWC (external wait cycles)?

(sprs880k.pdf; Table 5-38. EMIF Asynchronous Memory Switching Characteristics)

Regards,

  • 0
    TI__Guru** 116961 points
    Yoshita-san,

    If WAIT input is inactive then extended wait is not applied. Sorry, may be I did not understand your question properly. Can you explain it a bit more.

    Regards,

    Vivek Singh
  • 0 in reply to Vivek Singh
    TI__Genius 9095 points

    Hi Vivek,

    The case is assumed that no EMxWAIT input, even if Extended Wait Mode is enabled with register ASYNC_CS2_CR[30]=1.
    Or EMxWAIT signal has to be asserted as least one time in Extended Wait Mode?

    Regards,

  • 0 in reply to Vivek Singh
    TI__Genius 9095 points
    Hi Vivek,

    Could you please give some comments on it?

    Regards,
  • 0 in reply to ytakano
    TI__Guru** 116961 points
    Yoshita-san,

    If extended wait is enable then EMIF controller will extend the access time if EMxWAIT signal get asserted during access. If EMxWAIT is not asserted then it does not matter and access will terminate based on SETUP/STROBE/HOLD configuration.
    . Extended wait enable does not mean EMxWAIT has to be asserted. If Extended wait is disable then EMxWAIT input is don't care and controller will always terminate access based on the SETUP/STROBE/HOLD configuration.

    Hope this is clear.

    Regards,
    Vivek Singh
  • 0 in reply to Vivek Singh
    TI__Genius 9095 points

    Hi Vivek,

    > If EMxWAIT is not asserted then it does not matter and access will terminate based on SETUP/STROBE/HOLD configuration.

    My understanding is that;
    In case no assertion of EMxWAIT even if the register ASYNC_CS2_CR[30]=1,
    the parameter tw(EMWEL) will be defined as min:(WST+(EWC*16))*E–1 and max:(WST+(EWC*16))+1.
    The value of EWC will be minimum value as 1.

    Is my understanding correct?

    Regards,

  • 0 in reply to ytakano
    TI__Guru** 116961 points

    Yoshita-san,

    In case no assertion of EMxWAIT even if the register ASYNC_CS2_CR[30]=1,
    the parameter tw(EMWEL) will be defined as min:(WST+(EWC*16))*E–1 and max:(WST+(EWC*16))+1.
    The value of EWC will be minimum value as 1.

    No, this is only applicable if EMxWAIT is asserted.  Please see following note in datasheet.

    EWC is external wait cycle determined by EMxWAIT input signal. If EMxWAIT is not asserted then value of this will be '0'.

    Regards,

    Vivek Singh