What are the different access level of Arm Cortex-M0/3/4 Processor ?

 The Arm Cortex-M0/3/4 Processor has 2 access levels

1 - Privileged Access Level (PAL)

2 - Non-Privileged Access Level (NPAL)

In Privileged Access Level, the code to be executed has full access to all of the processor resources. In Non-Privileged Access Level, the code has restricted access to the processor resources and registers. By default, the code will run in Privileged Access Level. When the processor is in 'Thread Mode', it is possible to move the processor to Non-Privileged Access Level, but it is not possible to go back to the Privileged Access Level unless it changes first to handler mode. The access level of the 'Handler Mode' is always Privileged Access Level. Switching between Privileged Access Level and Non-Privileged Access Level can be done using the processor control register.

Written By: Musaab Taha