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MSP430F2274: tSBW,En clarification

Art Mecina
Genius 16505 points
Part Number: MSP430F2274

Hello Guys,

Good day.

Our customer is planning to use BSL Entry Sequence at Shared JTAG Pins of MSP430F2274. On the datasheet of the device, it was mentioned on Note (1) at page57 that Tools accessing theSpy-Bi-Wire interface need to wait for the maximum tSBW,Entime after pulling the TEST/SBWCLK pin high before applying the first SBWCLK clock edge.

Should not the 'maximum' read 'minimum'? Note that tSBW,Entime max is 1uS.

Thanks!

Art

  • 0
    TI__Genius 16505 points

    Hello Guys,

    Any update on this?

    Thanks!

    Art

  • 0
    TI__Mastermind 26420 points

    Hey Art,

    The datasheet appears to be correct, but I think I see the confusion. From the SBW Interface table in the datasheet

    "(1) Tools accessing the Spy-Bi-Wire interface need to wait for the maximum tSBW,En time after pulling the TEST/SBWCLK pin high before applying the first SBWCLK clock edge." 

    The data-sheet is saying that once TEST/SBWTCK is pulled high, the SBW tool must keep it high for at least 1 uS (the tSBW.En max time).  tSBW is the time it takes for the SBW module to become enabled, so to guarantee it's enabled on all devices you must always exceed this value. 

    So yes, SBWTCK should be brought high for a minimum or 1 uS. 

    Hope that clears it up. 

    Thanks,

    JD   

  • 0 in reply to JD Crutchfield
    TI__Genius 16505 points

    Thanks JD!

    However, the sentence in the datasheet SBW Interface table "(1) Tools accessing the Spy-Bi-Wire interface need to wait for the 'maximum tSBW,En time' after pulling the TEST/SBWCLK pin high before applying the first SBWCLK clock edge." should read 'minimum tSBW,En time' in order to make sense.

    When you 'have' to wait for something the wait time specified is implicitly a minimal time required. Of course, one can wait any other time longer the the minimal time :-) Thus the maximal time for waiting does not make sense.

    Best regards,

    Art

  • 0 in reply to Art Mecina
    TI__Mastermind 26420 points

    Hey Art,

    The confusion here is because the time period that needs to be met is literally defined as "maximum t_SBW,En time" in the table.  So the sentence should technically read  " (1) Tools accessing the Spy-Bi-Wire interface need to wait a minimum of 'maximum tSBW,En' time after pulling the TEST/SBWCLK pin high before applying the first SBWCLK clock edge.  

    I understand that this reads a bit confusing and maybe should be worded slightly differently, but the term 'maximum tSBW,En' is important.

    Thanks,

    JD   

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