This anomaly applies to Revision 1, build codes CLAA-D00, QKAA-D00.
Domains
Application, Network
Symptoms
Network core behaves erratically.
Conditions
This anomaly depends on the device and temperature and does not apply to all devices.
The anomaly can occur when the device is in the following state:
- Both application and network CPU are sleeping (WFI/WFE).
- Both cores are in Low-power submode.
- All peripherals are disabled or enabled and in IDLE state. The following peripherals can be in the listed states:
- LPCOMP is started.
- NFC is enabled and in SENSE_FIELD state.
- GPIOTE input is enabled.
- RTC is running.
- WDT is running.
- Network core peripheral or CPU is reacting to GPIOTE PORT event, RTC event, watchdog timeout, LFCLKSTARTED event, power-fail warning event, or SPIS/TWIS activity.
Failures are more likely to occur with short sleep durations and unlikely to occur with sleep durations longer than 150 ms.
The estimated failure rates for sleep durations shorter than 30 ms are the following:
- -40°C: On average 150 failures per one million wakeups with device variation between 0 and 100% failures per wakeup.
- -20°C: On average 50 failures per one million wakeups with device variation between 0 and 100% failures per wakeup.
- 0°C: On average 5 failures per one million wakeups with device variation between 0 and 50 failures per one million wakeups.
- +25°C: On average one failure per one million wakeups with device variation between 0 and 25 failures per one million wakeups.
Consequences
Network core CPU can hard-fault, trigger lockup reset, or become unresponsive. Network core can behave erratically.
Workaround
Use nRF Connect SDK version 2.5 or later.
The workaround provided in nRF Connect SDK consists of the following parts:
- Mechanism to ensure safe RTC wakeup from sleep
- Mechanism in application core for recovery
The implemented workaround uses system resources such as DPPI and IPC channels, RTC, and WDT. See nRF Connect SDK release notes for details.
Do not use the following network core wakeup sources:
- GPIOTE PORT event
- Wakeup from SPIS or TWIS
- Power-fail warning event
- LFCLKSTARTED event
The workaround implemented in nRF Connect SDK reduces the likelihood of the anomaly occurring but does not remove it completely.
With the mechanism to ensure safe RTC wakeup from sleep, the estimated failure rates for sleep durations shorter than 30 ms at -40°C to +25°C are on average 0.05 failures per one million wakeups with device variation between 0 and 20 failures per one million wakeups.
Use the recovery mechanism in nRF SDK version 2.5 or later to recover if a network core lockup reset occurs or the CPU is unresponsive.
Fix for this anomaly is scheduled to be included in the next hardware revision of the nRF5340 SoC.