This is a basic overview of the memory model used by the mbed RTOS.

Threads¶

Each thread of execution in the RTOS has its separate stack.

When you use the RTOS, before explicitly initializing any additional thread, you will have 4 separate stacks:

• The stack of the Main Thread (executing the main function).
• The Idle Thread executed each time all the other threads are waiting for external, or scheduled events. This is particularly useful to implement energy saving strategies. (ie sleep).
• The Timer Thread that executes all the time scheduled tasks (periodic and non periodic).
• The stack of OS Scheduler itself (also used by the ISRs).

      +-------------------+   Last Address of RAM
      | Scheduler Stack   |
      +-------------------+
      | Main Thread Stack |
      |         |         |
      |         v         |
      +-------------------+
RAM   |                   |
      |                   |
      +-------------------+
      |         ^         |
      |         |         |
      |       Heap        |
      +-------------------+
      | ZI                |
      +-------------------+
      | ZI: Idle Stack    |
      +-------------------+
      | ZI: Timer Stack   |
      +-------------------+
      | RW                |  
      +===================+  First Address of RAM
      |                   |
Flash |                   |