Hi @HugPeter-9392 , for the Cortex-M, ThreadX utilizes the automatic hardware stacking of the Cortex-M architecture. When a thread is interrupted, its stack is used (the "process stack"). Any nested interrupts use the "main stack" in "handler mode." There is nothing that you need to do to manage these stacks. The main stack address is placed in the first slot of the vector table. This main stack is set up in the linker file, so just make sure you are giving this stack enough memory to handle all your nested interrupts.