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Altera_Forum's avatar
Altera_Forum
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16 years ago

Bidirectional SPI switch?

This is a complex problem which I am very unsure of, the basic idea is that I want code that switches between 3 SPIs. I was startled when I noticed the statement that I was about to write ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

If I have understood you, you have A,B,C SPI interfaces and you want C to talk to either A or B:

(1) C to A or B

Since you have chipselect then you can drive both at same time then use chipselect.

(2) A or B to C: use your switch to drive C

This pseudocode may explain my idea: 


if OE = ?
    A <= C;
    B <= C;
    C <= 'Z';
else 
    A <= 'Z';
    B <= 'Z';
    if select = ?
        C <= A;
    else
        C <= B;
    end if;
end if;