Missed ticks meaning in Simulink Desktop Real-Time

Hi,

I have a really simple question. In all the Simulink Desktop Real-Time library I can find the word "tick", but I can't find an official explanation of its meaning.

I assume that a tick is the time length of the discrete solver, but for my real-time application I just want to be sure it is, because I need to evaluate the lag in millisecond the software could reach. So if it's correct I would just multiply the number of missed ticks lagging for the step length.

Thanks in advance.

Answer 1

[Jan Houska]

Hi Federico,

yes, your understanding is almost correct. A "tick" is an event when the real-time kernel tells a block that the time to execute is now. That is, if you miss one tick, the block is one sample period behind. But please note that this is related to the sample time of the particular block that provides the Missed Ticks output, not to the per-model discrete solver time step length. Although these are the same in many cases, this is by no means a rule and they can be and often are different.

Good Luck, Jan

[Federico Veronese]

Thank you Jan, so you are telling me that if the block says that is lagging by 1 tick, it means that it's for 1 of ITS sample time behind, and not for a sample time of the model (discrete solver) behind.

If my statement is correct I could find the time the system is lagging just by multiplicating the number of missed ticks of a block for the sample time of that particular block (and not for the sample time of the whole model/solver).

Thanks in advance, Federico.

[Jan Houska]

Yes, exactly.

Good Luck, Jan