| ??? 01/27/05 22:41 Read: times |
#85971 - Decisions, decisions Responding to: ???'s previous message |
Craig Steiner said:
That'd be impressive; but I'm curious as to how you get 8 tasks to require just 24 bytes of RAM? Aside from not protecting the stack, it would seem you're not protecting any of the "R" registers? Won't that lead to some nasty conflicts when tasks switch? Developing an RTOS for a resource limited micro inevitably means some tough decisions. However, the range of possible applications on such a micro is also limited. It is a cooperative despatcher so tasks run to completion and there is no need for stack protection. Timer0 is used for the tick with just TH0 reloaded in the ISR so the tick granularity is typically 0.25mS. Obviously the ISR saves the regs it affects. Each tasks needs three bytes of RAM. One is the offset from time zero in ticks after which the task is first scheduled. Next is a byte for the repetition period of the task. With a typical 4mS tick a byte value allows a 1 second period. The last byte is the run semaphore, set by the scheduler and reset by the despatcher along with a task enable/disable flag. At the moment inter-task communication and task state management is the responsibilty of the application. Ian |
| Topic | Author | Date |
| 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 |