Question about some conventions in IC pin names

Forum 2005-2010 (read only) Hardware Interfacing
1

Hello

What do the following mean in the context of pin names for ICs as found in data sheets

a forward slash prefix such as

/CS

a bar above a pin often with a pin of the same name without a bar on the same chip such as
__
Q7 and Q7
__
CE is another

(my question refers to why the additional symbols are used, not the abbreviations, I know for instance that CE is clock enable etc)

this symbol

Ø

also seen in the following sentence "1 MHz Ø2 clock"

and, finally, why is Q often used to signify data in/out pins?

Thanks
Jim

2

What do the following mean in the context of pin names for ICs as found in data sheets: a forward slash prefix such as /CS

This means the pin and/or signal is "active low". That is, it does whatever function it's named for when it's 0V, and it's idle/inactive when it's 5V. The \RESET pin on your Arduino, for example, is active low. When you connect it to 0V the Arduino resets.

The overbar indicates the same thing.

this symbol: Ø, also seen in the following sentence "1 MHz Ø2 clock"

I believe that refers to a 2-phase clock. Exactly what that means depends on the context.

As to why Q is used to signify data out pins....I'm not old enough to reach that far back :slight_smile:

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3

As to why Q is used to signify data out pins....I'm not old enough to reach that far back

Well I am old so let me give it a shot. I think it comes from the convention first used for simple flip-flop ICs (example 7474) where they labeled the two complementary output pins Q and /Q.

Lefty

4

Thank you gentleman