Embedded Talks Ep3 : Context Switching

Context switching refers to the process where cpu halt program currently executing save its context and switch to another process,Thing that can trigger context switch can be

• Hardware Interrupts

Context switching allows effectively run multiple tasks on a CPU allowing them to share, This effective switching gives illusion of running multiple process simultaneously at same time.

Process of Context Switch:

The process by which context is switched mainly involve saving information of general purpose register of currently executing program i.e Program counter, stack pointer etc and then restore when other job is finished, although seems simple it has to be optimized well for real time application

RTOS involvement:

Most embedded systems use a Real-Time Operating System (RTOS) to manage task scheduling and context switching, providing features like priority-based scheduling and cooperative multitasking.

Example scenario:

• A microcontroller is running a task to read sensor data while simultaneously monitoring a timer interrupt.
• When the timer interrupt occurs, the CPU saves the current state of the sensor reading task (its context).
• The CPU then executes the timer interrupt service routine, which might involve updating a system timer or triggering another task based on the time elapsed.
• After the interrupt service routine completes, the CPU restores the context of the sensor reading task and continues where it left off.