Kinetis Microcontrollers中的主题 volatile/auto variable access for Kinetis MPU (K8x)

volatile/auto variable access for Kinetis MPU (K8x)

muratcakmak — Sun, 08 Jan 2017 13:16:49 GMT

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?

muratcakmak — Sun, 08 Jan 2017 14:11:36 GMT

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

Problem is about GCC compiler.

jorge_a_vazquez — Fri, 13 Jan 2017 22:15:51 GMT

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