This anomaly applies to Revision 3, build codes QFAA-Gx0, QFAB-Gx0, CIAA-Gx0.
It was inherited from the previous IC revision
Revision 2.
Symptoms
The CPU is unexpectedly awoken from System ON Idle.
Conditions
The FPU has been used.
Consequences
The CPU is awoken from System ON Idle.
Workaround
The FPU can generate pending interrupts just like other peripherals, but unlike other peripherals there are no INTENSET, INTENCLR registers for enabling or disabling interrupts at the peripheral level. In order to prevent unexpected wake-up from System ON Idle, add this code before entering sleep:
#if (__FPU_USED == 1)
_set_FPSCR(_get_FPSCR() & ~(0x0000009F));
(void) __get_FPSCR();
NVIC_ClearPendingIRQ(FPU_IRQn);
#endif
__WFE();