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???
01/28/05 20:29
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#86053 - Worth it?
Responding to: ???'s previous message
Russell Bull said:

I really do question the need for a fancy task scheduler and computed calls for what is essentially a 'small system'. With most embedded systems, the tasks are known up front so therefore the address can be hard coded. similarly with scheduling the priorities are normally fixed - in most of my apps I use a co-operative tasker with a 10mS tick. I have up to 8 tasks of fixed priority. Each of these tasks has a timer that activates the task when it expires, the task can also be activated by calling "set_task". At each dispatch, the task run flags are evaluated for the highest priority to run, then that task is run for that tick. Whilst inter-task comms and semaphores are nice, they have a bit of overhead and a probably best left to a pre-emptive type RTOS. By definition - a co-operative task system need no interlocks since only one task can run at one time, and the task runs to completion. Sorry to pour water on your idea!

No worries. I agree with you. Your description pretty much agrees with what I am developing except your priority system is even more fancy than mine. Perhaps the only thing we disagree on is how to call each task. I too assume tasks are known up front, I just choose to hard code their addresses into a jump table indexed by task number.

Nowadays, if I want a pre-emptive type RTSO with semaphores and inter-task communication (pipes etc) - I wouldn't be choosing to use a 8051 type micro, most probsbly it would be ARM.

Again I agree. I never mentioned pre-emption and I specificaly said intertask communication was the responsibilty of the tasks.


Ian

List of 49 messages in thread
TopicAuthorDate
Computed Call            01/01/70 00:00      
   Computed Call            01/01/70 00:00      
   simulate an LCALL @A+DPTR instruction?            01/01/70 00:00      
   Solution            01/01/70 00:00      
      Computed LCALL            01/01/70 00:00      
      Computed LCALL            01/01/70 00:00      
         Table offset            01/01/70 00:00      
            x2, not x3            01/01/70 00:00      
   what is the problem            01/01/70 00:00      
      My Problem            01/01/70 00:00      
         never heard of it            01/01/70 00:00      
            It is.......            01/01/70 00:00      
               RTOS            01/01/70 00:00      
                  8051 RTOs Limitations/Issues/Opportunity            01/01/70 00:00      
                     How?            01/01/70 00:00      
                        Decisions, decisions            01/01/70 00:00      
                           Small systems - task scheduling            01/01/70 00:00      
                              Worth it?            01/01/70 00:00      
                                 Scheduler            01/01/70 00:00      
                                    Scheduler            01/01/70 00:00      
                           running small in a big way            01/01/70 00:00      
                              Example            01/01/70 00:00      
                                 in very small chips            01/01/70 00:00      
                                    In all sorts of sizes of chips            01/01/70 00:00      
                                       time dependednt            01/01/70 00:00      
                                          RTOS or Not            01/01/70 00:00      
                                             opinion piece            01/01/70 00:00      
                                                fact piece            01/01/70 00:00      
                                                Opinion piece            01/01/70 00:00      
                                             suggestion piece            01/01/70 00:00      
                                             reasons            01/01/70 00:00      
                                    Polite discussion            01/01/70 00:00      
                                       Politeness            01/01/70 00:00      
                                          Thanks            01/01/70 00:00      
                                             Politeness            01/01/70 00:00      
                                                What are you Rabbiting on about?            01/01/70 00:00      
                                                   Close but no Cigar            01/01/70 00:00      
                                                      Rabbit food            01/01/70 00:00      
                                                         Plessey            01/01/70 00:00      
                                                      small world            01/01/70 00:00      
                                                         Smaller than you imagine!            01/01/70 00:00      
            I use the computed LCALL ...            01/01/70 00:00      
               go it            01/01/70 00:00      
                  Call tabs in-line            01/01/70 00:00      
                     abbreviated            01/01/70 00:00      
                        ... and further optimized...            01/01/70 00:00      
                     has been already disscussed            01/01/70 00:00      
   Scheduler of course            01/01/70 00:00      
      Scheduler            01/01/70 00:00      

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