meaninig of __attribute__((persistent)) in MPLAB

[naderus]

__attribute__ mplab

Hi,

what is the meaninig of __attribute__((persistent)) in MPLAB?

 

[foxabilo]

mplab __attribute__

Classically (persistent) data reamins the same across multipul program restarts.

Translating that to the use in MPLAB it would indicate that the data defined in persistant will remain constant despite issuing a MCU reset, looking at the documentation this seems to be the case

# persistent data is not normally initialized by the C run-time. However, from a cold-restart persistent data may not have any meaningful value. This code example shows how to safely initialize such data:

#include "p24Fxxxx.h"

int last_mode __attribute__((persistent));

int main()
{
    if ((RCONbits.POR == 0) &&
        (RCONbits.BOR == 0)) {
      /* last_mode is valid */
    } else {
      /* initialize presistent data */
      last_mode = 0;
    }
}

seems to support that, although they point out a cold power reset may well reset the value which is understandable, basicaly persistent means that so long as the MCU has power no reset command will clear that data, only a cold start will.