https://devzone.nordicsemi.com/f/nordic-q-a/19758/nrf52832-sdk-s132-usagefault-exceptionHi, I want to implement handler for undefined instruction fault. According to Cortex M4 documentation (ARM DUI 0553A subchapter 2.3.2 &quot;Exception types&quot;) this fault leads to UsageFault exception. There is a HardFault_process weak function in SDK (S132en-USTelligent Community 13Thu, 16 Feb 2017 20:43:20 GMThttps://devzone.nordicsemi.com/thread/76835?ContentTypeID=1Thu, 16 Feb 2017 20:43:20 GMT137ad170-7792-4731-bb38-c0d22fbe4515:374b58de-1757-45f7-8214-535e936f6e61butch<p>At least for the GCC toolchain, see components/toolchain/gcc/gcc_startup_nrf52.S which is assembler code that defines the interrupt vectors and defines a weak UsageFault_Handler function which loops forever. Define your own implementation (and link objects/libraries in an order where your definition overrides the weak one?)</p> <p>If you mean the library that Nordic provides, cd to the nrf sdk directory and &quot;grep -R HardFault_process *&quot; will show you an implementation exists in components/libraries/hardfault/hardfault.h etc. And in Infocenter there is documentation about that library.</p><div style="clear:both;"></div>