1st : thanks for all answers ...

- Kim for the Microchip AN585 reference but, as far as I have read, it dealt
with interrupts ! ...
- Anyway, let's precise my aim for Barry King who asked me :

>Are you looking for a commercially built kernal?  Or are you looking
>for ideas on how to structure code to multi-task?
>
>If you are asking for ideas, we need to know more about what the tasks
>will do.  To multi-task without interrupts, you will end up with a
>main loop which calls the tasks, or portions of them.  The taks must
>be structured to run for some time, then let another task run. And
>there will usually be some other code to coordinate any shared
>variables or communication between the tasks.
>
>Two important things are to know how the tasks must communicate, and
>whether there is hardware that they must share.  Also, it is
>important to know what latency is acceptable, that is, how long can
>one of the tasks be stopped before it fails?

I'm looking for ideas for a specific project :

I have to check for serial inputs while out-puting one or more PWM depending
on the input(s).

In fact, my first application should be an attempt to read 1 RC pulsed
command, ie :

1) Measure the "n"st positive pulse among 7 overall pulses ; synchro being
made by a 1st larger pulse and length of the usefull pulse varying between 1
and 2 ms ; overall time = 10 to 20 ms

2) While outputing a PWM at 10 to 100 Hz, from #0 to #100% duty cycle

3) That's all !

4) I've thought of an absolute timing that each individual task could check
and determine if their allowed time have passed. That shouldn't be very
accurate but enough for me ?

Thanks for any other comment !