A problem about the Sample Time in the asynchronous subsystem

Hi, There is a subsystem in my model.The model's sample time is 0.0001,and i want to set some block's sample time in the subsystem 0.0005.But when i click the build button ,i got the error as follows:

Error building Real-Time Workshop target for block diagram '2812_StepTime'. MATLAB error message: '2812_StepTime/Function-Call Subsystem/Counter Limited/Output' has an invalid sample time. Only constant (inf) or inherited (-1) sample times are allowed in the asynchronous subsystem '2812_StepTime/Function-Call Subsystem/Counter Limited'

How could solve this problem?

My matlab version: 2009a

Best regards.

Answer 1

[Titus Edelhofer]

Hi,

this can't work: you call you subsystem with a function call asynchronously, so blocks inside the subsystem have no "direct" control about when the subsystem is called. How could a block inside impose a sample time? It would need to carry this information to the containing subsystem... Perhaps you could explain in more detail why a block inside the fcn call subsystem should have a fixed sample time...

Titus

[w w]

The subsystem is called by a Hardware Interrupt block.If the blocks in the subsystem should be with different,is there any ways to solve ths situation?

[Titus Edelhofer]

One way to overcome many problems: move the offending block outside the subsystem and feed the output of the block as an input to the subsystem (probably using a rate transition block in between). Further advice is I guess only possible with more information aout why you want to have a fixed sample time block in your subsystem.

Answer 2

[Fangjun Jiang]

It makes sense, right? Your "2812_StepTime/Function-Call Subsystem/" is a function-call system, which could be called irregularly, depending on where the function call trigger comes from. Thus, it can not guarantee the inside block "Counter Limited/Output" be called in a fixed rate.

It sounds like you are using a function call generator block with a fixed sample rate. Why not try to specify your subsystem as an atomic subsystem with a fixed sample rate of 0.0001. I believe that will get rid of the error.

[w w]

The subsystem is called by a Hardware Interrupt block.So i could not use the atomic subsystem.