Multitasking in AVR (A demo to run 7 tasks on an atmega32)

Hi,
Here I am introducing a simple task switching on an AVR as a demo... I did this just to get familiarized with the AVR assembly language programming.. Now I believe I learned it to an extent. Also I loves assembly language because it offers a great deal of power to use all of the features of the processor.

Introduction:

     Switching multiple tasks on a same CPU is the one of the major function of an operating system. What I did now is a time sharing multitasking (time multiplexing) on an AVR. Here an atmega32 is configured to use Round-Robin Multitasking. Round-Robin allows quasi-parallel execution of several tasks. Tasks are not really executed concurrently but are time-sliced (the available CPU time is divided into time slices). 

         Here, in my code below, it consist of 7 independent tasks and those are switched from one to another on a timer interrupt. 'May be' this could be considered as a simple & very very basic RTOS demo. Here I am mainly focusing on the core part ie the "task switching". 

Scheduling algorithm used: Round-robin (RR)
(one of the simplest scheduling algorithm)

Video demo:

Each led on the demo represents a task. Task1 (right most led, WHITE) is a software PWM task. All other tasks (2 to 7 from right to left) are toggling tasks. If you concentrate on a single LED, U may notice that the particular LED is toggling with a constant delay and is independent of others.

Working: 

 Here, total RAM (2KB) is divided among 7 tasks almost equally in such a way that each one get around 300 bytes of RAM space... This 300 bytes is considered

MULTITASKING IN MSP430

Task switching is one of the main function of an operating system. We could 'feel' a computer is doing multiple tasks at a time. The OS is actually switching the tasks one by one in a circular manner and executing each one for a small period of time and we feel it is doing all tasks at a time.... 

A small demo of multitasking in MSP430G2231 microcontroller:

     Here, three independent tasks are to be switched on every timer interrupt.  The CPU registers used in previous task is to be stored some where and the register values of the task to which it is switched is to be retained as before. Also, the switched task should run from where it is paused earlier.

Below is my asm code for running three independent tasks in an MSP430G2231 microcontroller. (just a demo, stack depth is very limited due to the limited RAM)