Understand fault handler

Mbed OS
10

thank you for all the advice so far!
so I’ve now been able to get the parser to work and have the following output

Crash Info:
        Crash location = SHT$$INIT_ARRAY$$Limit [0xFFFFFFFF] (based on PC value)
        Caller location = SHT$$INIT_ARRAY$$Limit [0xFFFFFFFF] (based on LR value)
        Stack Pointer at the time of crash = [1FFFDBE4]
        Target and Fault Info:
                Processor Arch: ARM-V7M or above
                Processor Variant: C24
                Forced exception, a fault with configurable priority has been escalated to HardFault
                MPU or Execute Never (XN) default memory map access violation on an instruction fetch has occurred

I think I understand the that most important information is:

MPU or Execute Never (XN) default memory map access violation on an instruction fetch has occurred

and the lines of my code it gets angry at are:

 if (diffx[store] >= 0) { dirPin[0] = 1; }
 else if (diffx[store] < 0) { dirPin[0] = 0; }
 if (diffy[store] >= 0) { dirPin[1] = 1; }
 else if (diffy[store] < 0) { dirPin[1] = 0; }

does anyone know why this might cause this error to occur?

many thanks
George