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56xx SWT Configuration

Question asked by Andrew Smith on Oct 20, 2017
Latest reply on Oct 20, 2017 by Peter Vlna

Can anyone suggest a reason as to what's wrong with this attempt to configure the SWT on a 56xx device.


On entry to the code SWT.CR.R = 0xFF00010A - so watchdog is disabled and SLK is cleared.


#define SWT_UNLOCK1      0xC520
#define SWT_UNLOCK2      0xD928
#define SWT_5MSTIMEOUT   0x13880     /* 16MHz Internal osc..@5ms timeout => 16MHz/200 = 80000 = 0x13880 */
#define SWT_SLK          0x00000010  /* Mask for software lock bit */
#define SWT_WEN          0x00000001  /* Mask for watchdog enable bit */


 /* Routine to setup software watchdog timer */
 /* If watchdog is disabled - set it up, otherwise leave it alone */
 if (!(SWT.CR.R & SWT_WEN))
    if (SWT.CR.R & SWT_SLK)
     /* Soft lock bit is on - unlock the control register */
     /* Unlock the control register */
        SWT.SR.R = SWT_UNLOCK1;
        SWT.SR.R = SWT_UNLOCK2;

    /*  Wait here for SLK to clear */
    while(SWT.CR.R & SWT_SLK);
    /* CR should now be writable  */
    SWT.CR.R |= SWT_WEN;
    /* Set timeout interval */


On exit of this code, the SWT.TO register has been updated, but no matter what I do to write to SWT.CR (including, for instance SWT.CR.R = 0xFF00010B;) the watchdog remains disabled.


Any idea why this is?


Thanks for any suggestions.