In ARM processors, an exception causes different processor state switching and different register contents to be pushed on the processor stack than for a 'normal' interrupt.
The most common ARM processor exceptions include data abort exceptions, undefined instruction exceptions, and prefetch abort exceptions. With a 'normal' interrupt, some basic stack/register operations must be performed and the interrupt cleared in the VIC (Vectored Interrupt Controller) to resume normal operation. With a processor exception, there may not be a safe or easy way to attempt to resume where the processor had left off, and often one has to try to gracefully cleanup and prepare to reboot/restart the processor (get a "clean slate"). One method of doing this is to make the processor watchdog timer reset the processor.