Posted on July 20, 2017 at 06:26Hi ,
I ran into a lockup issue after FAULTMASK is set by cpsid f. The software is running in SDRAM, and MPU is enabled, so instruction can be executed from SDRAM. At last, I found the lockup issue is gone if HFNMIENA bit is set. But I don't fully understand why from the
STM32F7 Series Cortex�-M7 processor programming manual(PM0253):
HFNMIENA bit description:
Enables the operation of MPU during hard fault, NMI, and FAULTMASK
handlers.
When the MPU is enabled:
0: MPU is disabled during hard fault, NMI, and FAULTMASK handlers,
regardless of the value of the ENABLE bit.
1: The MPU is enabled during hard fault, NMI, and FAULTMASK handlers.
When the MPU is disabled, if this bit is set to 1 the behavior is
Unpredictable.
Unless HFNMIENA is set to 1, the MPU is not enabled when the processor is executing the handler for an exception with priority �1 or �2. These priorities are only possible when handling a hard fault or NMI exception, or when FAULTMASK is enabled. Setting the HFNMIENA bit to 1 enables the MPU when operating with these two priorities.
From the description, does that mean
FAULTMASK is set will cause MPU is disabled if
HFNMIENA bit is cleared?
#mpu #faultmask #stm32f7
