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CC2652RB: Is Sensor Controller SRAM retained during a hard reset?

Chris Hunt
Intellectual 945 points
Part Number: CC2652RB

The CC2652RB datasheet mentions the Sensor Controller and resets in a couple places.  First in section 9.4 Memory, on page 51:

There is a 4-KB ultra-low leakage SRAM available for use with the Sensor Controller Engine which is typically used for storing Sensor Controller programs, data and configuration parameters. This RAM is also accessible by the system CPU. The Sensor Controller RAM is not cleared to zeroes between system resets.

Then again in table 9-1 Power Modes in section 9.12 Power Management, on page 55:

"System reset" does not appear to be defined in this document, nor is it even mentioned anywhere else, so it's not clear whether that's limited to software or not.  Obviously a power-on reset wouldn't be expected to preserve volatile memory, but the reset pin seems like it could go either way.  Does "Off" mean that the Sensor Controller is just unavailable/not running, or unpowered with no SRAM retention?

  • +1
    Expert 2160 points

    Hi Chris,

    SRAMs are powered off during hard resets and thus not designed to retain content. However it may actually retain data for some time after puling reset low and since the RAM is not cleared to zeroes you should be able to use that data after reset. TI will never vouch for relying on this, so you are basically left to your own testing to judge if you can rely on this or not in your product or not. 

    For some older CC26xx devices where the main SRAM was not cleared to zero, TI was actually storing data in SRAM during reset when switching firmware for OTA :-)

    /F

  • 0 in reply to fredrikgk
    Intellectual 945 points

    Thanks for both the official and unofficial answers!  We'll see what we can do with it then.