Implementing a discrete buffer, i.e. a Memory Block with multiple frames

Dear Forum,

I really like the memory block in matlab to store a single value from the previous frame in a fixed-step discrete simulink simulation. However, is there any way to have a "memory block" with more than one sample of memory? For example, buffering the last 3 samples, and then being able to extract any of the three samples I want?

I have successfully done this using a persisent and preallocated matrix in a matlab function block. This is okay, bbut coding it is clunky, and it slows down my simulation. Is there any built-in solution?

Here is the matlab code that I would like a built in solution instead of:

%% matlab code inside a MatlabFunction block. REALLY SLOW!
%last in first out
function y=LIFO(u,bufferSize)
    persistent buffer
    if (isempty(buffer))
        buffer=zeros(1,bufferSize)
    end
    y=buffer(1)
    for i=1:bufferSize-1
        buffer(i)=buffer(i+1)
    end
    buffer(bufferSize)=u
end

Answer 1

[Jonas]

Here is example code for storing the last 10 samples. Of course, you can adapt to memorize more history samples.

Summary: Use a Unit Delay block and feed it into a Selector block. The Selector block selects the (1:9) samples (so discarding the last one). Using a mux, we put these 9 samples at the end, and a new sample at the beginning. Then, the Unit Delay saves the 10 samples again to feed it back to the Selector.

Please see attached model made in r2020b.

[Michael Sohnen]

I might try it. Thanks!