Data Sheet

1051
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
Do not use the WCOMP interrupt. Use the WCOMP event.
39.2 Device Variant B
39.2.1 Revision E (Only available for SAMD21x15/16)
1 - SYSTICK calibration value is wrong. Errata reference: 14155
Fix/Workaround:
right SYSTICK calibration value is 0x40000000.
2 - On pin PA24 and PA25 the pull-up and pull-down configuration is not disabled
automatically when alternative pin function is enabled. Errata reference: 12368
Fix/Workaround:
For pin PA24 and PA25, the GPIO pull-up and pull-down must be disabled before enabling
alternative functions on them.
3 - If APB clock is stopped and GCLK clock is running, APB read access to read-
synchronized registers will freeze the system. The CPU and the DAP AHB-AP are stalled, as
a consequence debug operation is impossible. Errata reference: 10416
Fix/Workaround:
Do not make read access to read-synchronized registers when APB clock is stopped and GCLK is
running. To recover from this situation, power cycle the device or reset the device using the
RESETN pin.
4 - In I2C Slave mode, writing the CTRLB register when in the AMATCH or DRDY interrupt
service routines can cause the state machine to reset. Errata reference: 13574
Fix/Workaround:
Write CTRLB.ACKACT to 0 using the following sequence:
// If higher priority interrupts exist, then disable so that the
// following two writes are atomic.
SERCOM - STATUS.reg = 0;
SERCOM - CTRLB.reg = 0;
// Re-enable interrupts if applicable.
Write CTRLB.ACKACT to 1 using the following sequence:
// If higher priority interrupts exist, then disable so that the
// following two writes are atomic.
SERCOM - STATUS.reg = 0;
SERCOM - CTRLB.reg = SERCOM_I2CS_CTRLB_ACKACT;
// Re-enable interrupts if applicable.
Otherwise, only write to CTRLB in the AMATCH or DRDY interrupts if it is to close out a
transaction.