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Last Post 02 Feb 2012 03:55 PM by  loginreg@gmail.com
Use MSTR_nRST or SYS_nRESWARM? Why go against the TI docs?
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loginreg@gmail.com
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31 Jan 2012 05:52 AM
    I see that the LPD Hardware spec recommends using MSTR_nRST to reset the SOM.

    But the TI docs recommend using SYS_nRESWARM to reset the SOM.

    Looking at the schematic it is clear that LPD has designed the board to be able to be reset by using the MSTR_nRST (with the 1k resistor in series). Also it is still possible to use the TI scheme and use SYS_nRESWARM.

    So my question is: Why did LPD deliberately design the SOM for reset with MSTR_nRST? Is there some particular reason that SYS_nRESWARM is not a suitable source of reset? Are the TI docs just wrong about the reset? Will I experience problems by using the TI reset scheme?

    I ask because I am designing the base board and need to know why I should go against the TI docs and instead use the MSTR_nRST.
    richard.laborde@logicpd.com
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    02 Feb 2012 02:37 PM
    reg,

    The response I got from the HW guys is that the baseboard was used for a different product before, so we had a policy of using the RESPWRON to do a hard reset of the processor. It has been noted that this can cause issues coming out of very low power states.

    From the HW team:
    **
    I would suggest the customer pay attention to the different interfaces that are reset during POR and warmreset to decide which button they want to use; noting that our software is set up to handle things the way we have our baseboard routed.
    **

    Thanks
    loginreg@gmail.com
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    02 Feb 2012 03:55 PM
    Okay. So since it appears to be for legacy reasons only that the power-on-reset is used then I will use the TI recommended scheme and use the warm-reset.

    I also checked on some other SOMs from other manufacturers and all of the ones I saw use warm-reset. So I am happy to use the warm-reset signal as it appears to be working well and I can't find any negative information about it doing a web search.
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