Memory watch unit

A microcontroller (1) comprises a processor (2), a memory (3), a bus (15) connecting the processor (2) and the memory (3) and a memory watch unit (14), comprising one or more memory-watch event registers and one or more configuration registers. The memory watch unit (14) is arranged to monitor memory access instructions on the bus (15), and can be configured, using the one or more configuration registers, to (i) detect a memory access instruction for a memory address in a configurable watch region of the memory (3), and (ii) change the contents of one or more memory-watch event registers in response to such a detection.