Enabling usage_fault exception with division_by_zero fault

amigneault — Wed, 09 Jun 2021 13:54:45 GMT

Hi, I am developing on a FRDM-K66F and I am trying to trap floating point exception by generating an interrupt.

I understand that it should be a usage fault interrupt that will be triggered.

The sample code below show that I am enabling the usage_fault interrupt, I set a priority then I enable all possible floating point exceptions in the Interrupt Status Register (MCM_ISCR) .

If I run this part of code, after the div/0 I see that the MCM detect it because if I read MCM_ISCR back I see 0x9F120200, FDZC is now set as well as the FPSCR[DZC].

Question: What am I missing to generate the interrupt? Code goes through, never calling the ISR (which is a while(1) for now.

float toto=1.0;

SCB->SHCSR|=SCB_SHCSR_USGFAULTENA_Msk |SCB_SHCSR_BUSFAULTENA_Msk |SCB_SHCSR_MEMFAULTENA_Msk;

NVIC_SetPriority (UsageFault_IRQn,0x08);

*(uint8_t *)0xe0080010=(uint8_t)0x9F;

toto=toto/0.0F;

Thanks

Re: Enabling usage_fault exception with division_by_zero fault

Omar_Anguiano — Fri, 11 Jun 2021 20:23:40 GMT

Hello

Please add these lines to enable the registers:

NVIC_EnableIRQ(UsageFault_IRQn); SCB->CCR |= (SCB_CCR_DIV_0_TRP_Msk); SCB->SHCSR|= SCB_SHCSR_USGFAULTENA_Msk |SCB_SHCSR_BUSFAULTENA_Msk |SCB_SHCSR_MEMFAULTENA_Msk;

The reason why the interruption is not detected is the line "toto=toto/0.0F;"
If you add this function to your code we can see that the Usage fault is called:

static int _DivideByZero(void) { int r; volatile unsigned int a; volatile unsigned int b; a = 1.0; // movs r3, #1 <- Load dividend b = 0.0; // movs r3, #0 <- Load divisor r = a / b; // udiv r3, r2, r3 <- divide by 0 raises fault exception return r; }

If you have more questions do not hesitate to ask me.
Best regards,
Omar

Processor Expert SoftwareのトピックEnabling usage_fault exception with division_by_zero fault

Enabling usage_fault exception with division_by_zero fault

Re: Enabling usage_fault exception with division_by_zero fault