Strange electronic symbol in the

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Hello,

In the Atmel documentation "8-bit Microcontroller with 4/8/16/32K Bytes In-SystemProgrammable Flash / ATmega48PA, ATmega88PA, ATmega168PA, ATmega328P" (http://www.atmel.com/Images/doc8161.pdf), on page 76, "General Digital I/O" structure, there is an electronic symbol that I do not understand. Could you tell me exactly what the "four branch star" symbol means? Is it a standard symbol?

Olivier

 

 

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For the benefit of others he means...

 

http://www.avrfreaks.net/sites/default/files/forum_attachments/Atmel-IO.PNG

I cut that symbol from this image and did a google image search with it. No visually similar images were found so I think this may be unique to Atmel.

 

It clearly seems to be some kind of gate to switch direction of the signal according to "SLEEP" but what it actually is seems a bit of a mystery?

 

BTW @OP you don't have to "attach" images on this site like the old one - you can just paste them into this editor which is what I've done with your attachament. In fact I just opened it in another browser tab and drag/dropped it into this post. You can then double-click it and set things like scaled size and so on. (I set it to 600 wide).

Last Edited: Mon. Nov 10, 2014 - 10:45 AM
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It's a cmos transmission gate - analog switch effectively. 

Google cmos transmission gate symbol

If SLEEP is low, the signal from the left is coupled to the output buffer

If high, the output is clamped low by the mosfet.

Last Edited: Mon. Nov 10, 2014 - 10:54 AM
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it's a transmission gate.

 

Ok to slow

look at 4016 and 4066

Last Edited: Mon. Nov 10, 2014 - 11:00 AM
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Ah, it's an analog switch! Thank you for your answer, I had never met that symbol. For completeness, I may cite these two drawings from the article "What is a Transmission Gate (Analog Switch)?" from Maxim Integrated (http://www.maximintegrated.com/en/app-notes/index.mvp/id/4243)

Analog switch

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As others have noted, it is a transmission gate = bidirectional analog switch. It was used by RCA back in the early CMOS days, CD4066 and such. It is made up of two buffer triangles, superimposed, facing opposite directions since it is bidirectional.

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net