Timer SAMD21 sleep mode

Hi all,
I'am working on a samd21e18a, I use Adafruit wrapper for timer here but I'd like to let a timer running in a deep sleep mode but it's doesn't work, I added this in my setup but it's seem it's not working, should I set another clock to run in stand by mode?

SYSCTRL->XOSC32K.bit.RUNSTDBY = 1;

As you suspected, you also need to set the 48MHz Digital Frequency Locked Loop (DFLL48M) clock and TC timer's RUNSTDBY bits.

For the DFLL48M clock:

SYSCTRL->DFLLCTRL.bit.RUNSTDBY = 1;   // Set the DFLL48M 48MHz clock to run on standby
while(SYSCTRL->PCLKSR.bit.DFLLRDY);   // Wait for synchronization

For the TC timer you'll need to first disable it, (since the timer's CTRLA register is enable-protected), set the RUNSTDBY bit then re-enable. You'll also need to select which timer you're using TC3, TC4 or TC5 and the timer size 8, 16 or 32-bit, for example TC4 in 16-bit timer mode:

TC4->COUNT16.CTRLA.bit.ENABLE = 0;           // Disable timer TC4
while (TC4->COUNT16.STATUS.bit.SYNCBUSY);    // Wait for synchronization
TC4->COUNT16.CTRLA.bit.RUNSTDBY = 1;         // Set timer TC4 to run on standby
TC4->COUNT16.CTRLA.bit.ENABLE = 1;           // Enable timer TC4
while (TC4->COUNT16.STATUS.bit.SYNCBUSY);    // Wait for synchronization

@simon884 By the way, if you need run a number of timers or peripheral in standy mode, you'll also need to keep the SAMD21's internal voltage regulator activated as well:

SYSCTRL->VREG.bit.RUNSTDBY = 1;    // Keep the voltage regulator in normal configuration during run stanby