Command Handling When a command arrives from the SCU (via the 1553 interface) or the ICU (via the SSI interface), the respective ISR will enqueue the command packet into a Command Queue, and then give the semaphore to awaken the ccmCmdTask().  Since it is possible for the DPU to send a command to itself, commands may arrive at interrupt context or task context.  Therefore the CCM maintains two queues – one for interrupt context which is not semaphore protected, and one for task context which is semaphore protected.