What is this thing called? how does it work? I've tried googling so much, even pasted the image in the google search box haha

unknown gate

Its used here on the MSP430:

enter image description here

  • 1
    \$\begingroup\$ I gather you are more of a programmer type. Datasheets for pretty much all of the microcontrollers include diagrams like that. And it is very important that you are competent reading them. If the text in the datasheet differs from what you see in the diagram, chances are the diagram is right and the text is wrong. I suggest you get a copy of the free program called Logisim. Learn to use it, play with a few things there. It's a lot of fun and it will help deepen into you how to read these diagrams more fluently. You will see it includes a mux, like your picture above. \$\endgroup\$
    – jonk
    Nov 23, 2016 at 2:41
  • \$\begingroup\$ Yep, programmer through and through. Thanks for you help and advice! \$\endgroup\$
    – Jered
    Nov 23, 2016 at 2:44
  • 3
    \$\begingroup\$ Well, I'm very glad to see you struggling to read the diagrams! I've been doing embedded programming all my life. And I've been an employer of as many as 45 programmers (Summa Tech.) For embedded work, I may hire a programmer who couldn't read a diagram (I don't hire on one issue alone) but I'd think twice about it and if I did hire them I'd do so with a plan to train them quickly. I think its very much in your favor that you are asking questions like this!! Keep it up. \$\endgroup\$
    – jonk
    Nov 23, 2016 at 2:49

2 Answers 2


It's a multiplexer. When the input on the side has a specific value, the input corresponding to that value is propagated to the output. It's not a single gate per se but rather is composed of several gates that implement the function.


I's a multiplexer.

Logically it is the same as the following circuit:


simulate this circuit – Schematic created using CircuitLab


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