volatile/auto variable access for Kinetis MPU (K8x)

[muratcakmak]

Hello,

Interestingly, volatile and auto variables show different behaviours with Kinetis Custom MPU HW module.

BUS fault is rised only with volatile variable access. Please see following combinations.

#define RESTRICTED_ADDRESS       0x2001000

/* OK! Rises BUS Fault */

volatile uint32_t val = *(volatile uint32_t*)RESTRICTED_ADDRESS;

/* OK! Rises BUS Fault */

volatile uint32_t val = *(uint32_t*)RESTRICTED_ADDRESS;

/* OK! Rises BUS Fault */

uint32_t val = *(volatile uint32_t*)RESTRICTED_ADDRESS;

/* UPS!!!!!!!!!!!!!!! No BUS Fault Exception, continues to execution */

uint32_t val = *(uint32_t*)RESTRICTED_ADDRESS;

Any idea? Any limitation on Kinetis Custom MPU?

[jorge_a_vazquez]

Hi Murat Cakmak

Could you tell us what IDE and MCU are you using? I have tried to replicate what you mention but in my case it rises BUS Fault as expected.

Regards

Jorge Alcala

[muratcakmak]

The other interesting thing is when build project with ARMCC, it works as expected.

Problem is about GCC compiler.