How to force nrf52840 (with cortex m4) to have precise bus error

[erlendwit]

Hey!

From this link it says one can force the cortex-m4 to disable write buffering. This is supposed to remove imprecise bus errors.

To do this i write 1 to bit 1 in the ACTLR using this code 

	#include "core_cm4.h"
	volatile SCnSCB_Type *ptr_scnscb;
	ptr_scnscb = (SCnSCB_Type *)0xE000E000;
	ptr_scnscb->ACTLR |= SCnSCB_ACTLR_DISDEFWBUF_Msk;

However I still get imprecise bus errors and cant find the true cause, so what am I doing wrong?

Thanks!

[Vidar Berg]

Hello,

This may not be very helpful, but I was able to go from a imprecise busfault to a precise busfault after I added your code to my main().

Crash log before setting the DISDEFWBUF bit:

And after:

Code triggering the bus fault in both cases:

Maybe it could be worth checking if the DISDEFWBUF bit is still set after the fault exception is raised?