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I want verify 2nd case of the below truth table of MAX485 IC (RS485). Please see in red color.enter image description here

Is my circuit correct ? I have connected RE,DE and A-B to GND for making it LOW.I have connect DI to GND also just to avoid floating connection. However LED still unexpectedly blinks. why?

schematic

simulate this circuit – Schematic created using CircuitLab

what is wrong in my cicuit?

thanks

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  • \$\begingroup\$ This is basically same as your previous question? \$\endgroup\$
    – Justme
    Commented Oct 31, 2020 at 16:42

1 Answer 1

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Since both A and B are 0V, 0V-0V=0V difference between them. The difference does not exceed threshold of logic 1 or logic 0 (+0.2V or -0.2V) so the fail-safe mechanism keeps the RO high.

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  • \$\begingroup\$ how can i create difference of A-B = 0.2v between pins A and B? \$\endgroup\$
    – Ravi
    Commented Nov 1, 2020 at 8:03

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