Re: [AVR-Chat] Re: WinAvr or CodeVision, which one is more public?
2008-01-22 by subscriptions@aeolusdevelopment.com
David VanHorn Wrote >> U talked of RTOS. Never heared of it before, but my MCU needed to >> control RH, light level and temperature real time and show them on >> LCD, so I thought and then I made for myself a sort of virtual multi- >> tasking procedure, for example: >> >> Do >> Gosub v >> Gosub w >> Gosub x >> Gosub y >> Gosub z >> Loop >> End >> > >This is the guts of a cooperative multitasker. A simple co-operative multitasker. This particular kind is often referred to as a super loop and is simple enough that some object to it being referred to as a multitasker. They prefer to think of it as a single task state machine. There is a grey area here. Time for a little RTOS taxonomy I think RTOS's can be classified as pre-emptive or co-operative single stack (run to completion) or multiple stack round-robin or priority There are other characteristics but I think these are the most important and these characteristics are independent. Independence does not mean you can change just one item in any particular implementation just that you can implement any combination. The above is a co-operative, round-robin, single stack multitasker. pre-emptive systems bring in the ability to interrupt the current task at any time but also need to be able to protect critical sections from being interrupted by other tasks. Co-operative systems generally remove the need to implement as many safeguards but their responsiveness and the granularity of tasks falls completely on the programmers shoulder showing up in the task breakdown itself. Single stack systems use only a single stack (obviously) and thus have simpler memory management and task switching. Multiple stacks allow tasks to block waiting for resources or data. Round-robin provides simple fairness. Priority based allows more frequent and/or more important tasks first access improving responsiveness if done correctly. Other characteristics include types of IPC, memory allocation, device driver model (if any), task creation .... Robert -------------------------------------------------------------------- myhosting.com - Premium Microsoft® Windows® and Linux web and application hosting - http://link.myhosting.com/myhosting