In my day job and free time I frequently find myself debugging Arm Cortex-M microcontrollers (MCUs). In recent years, it has become more and more common for the cores in these MCUs to implement Armv8-M, with the Arm Cortex-M33 being a very popular variant. Armv8-M includes an optional security extension (Cortex-M Security Extension or “CMSE”), which is more commonly known by its marketing name, TrustZone. The security extension allows for a core, or a Processing Element (PE) if using the official terminology in Arm reference manuals, to divide memory into Secure and Non-Secure regions.