# Question Regarding IC pin numbering and logic gates

• Temp0
In summary, you need to determine the pin numbers for the inputs and outputs of the logic gates you will be using, and then wire them together according to the diagram.
Temp0

## Homework Statement

http://i.imgur.com/k8nq4HZ.jpg
So I need to assign IC pin numbers to the input and output of the logic gates.

None

## The Attempt at a Solution

I only have limited knowledge on integrated circuits as a whole, so I'm pretty confused altogether. I know that I can hook up inputs and outputs onto my IC, and then produce a result, but how do I know which pin numbers to use?

Edit: I learned a bit more about integrated circuits and logic gates over the internet, so I understand that each integrated circuit has a built in system of logic gates, and the pins represent either input, output, ground, or voltage source. However, I am still confused about what to do for this, I know that I'll probably be using multiple integrated circuits and using wires to replicate the situation in the picture, but I'm confused about a few things.
On a breadboard, what exactly is A, B, Cin, S, and Cout?
Also, is this assignment as simple as I think it is? Just wiring together integrated circuits according to the diagram?

Last edited:
Your picture shows a series of logic gates. look up logic symbol images, to see the differences. If you have a specific IC chip in hand that you know has these specific logic gates, then you have to determine which pairs of pins correspond to what types of gates.

While it has been a while since I played with logic chips, the ones I remember were of a type- one chip was all AND gates, another was OR gates, and so on. if this is the case, you will need a set of chips, then get each ones' pin-out configuration, and that will point you toward the wiring of them.

As for the letters; while I do cannot know what specifically they refer to in your situation, by the setup, A and B are choices (maybe switches, push buttons, etc) that determine if Cin reaches Cout or S is enabled.

Reading the logic shown from left to right and top down should enable you to determine what outcome you get for a given input. for example: If you choose ONLY A or ONLY B or ONLY Cin, you get S. any combination of two or three of the options negates that possibility - that comes from the two XOR (exclusive OR) gates at the top. Similarly you can determine what specific set (or sets) of selections allow for Cout to occur.

Hope this helps, and does not state what you already know. *grin*

1 person
Logic gates are available in many different forms. Have you been told what family of devices to use or what technology?

For decades you could/can buy logic gates in "packages" of 2 to 8 gates all of the same type on one chip. A common family is the 7400 series...

http://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuits

See the table.

For example a 7402 contains four NOR gates, each having two inputs and one output.

If you look at the data sheet for it will give you the pin numbers for the inputs and outputs.

Remember that the inputs of unused (spare) gates should not be left unconnected.

PS: In general it doesn't matter which of the gates within a package you use. However sometimes you choose one instead of another in order to make the external wiring easier/shorter. For example when connecting the output of one gate to the input of another (of the same type) it helps if they are in the same package and/or the pins are adjacent.

1 person
Thank you for all your help, combined with my questions to the professor and the knowledge I found on the internet, I successfully completed my task of building a one-bit full adder in the lab. Tons of wires running around everywhere, but I got it done.
Thanks again.

Well done. That's quite a complex "first circuit" to build. I think mine was a lot simpler.

## 1. What is the standard pin numbering for ICs?

The standard pin numbering for ICs follows a counterclockwise numbering scheme, starting from the top left corner. This means that the first pin on the top left is numbered as pin 1, and the numbering continues in a counterclockwise direction.

## 2. How do I determine the input and output pins on an IC?

The input and output pins on an IC can usually be determined by looking at the datasheet for the specific IC. The datasheet will usually have a pinout diagram that shows which pins are inputs and which are outputs. Additionally, input pins are usually marked with an "I" or "IN" while output pins are marked with an "O" or "OUT".

## 3. Can I connect inputs and outputs on different sides of the IC?

No, it is not recommended to connect inputs and outputs on different sides of the IC. This can cause problems with signal propagation and can potentially damage the IC. It is best to keep all inputs and outputs on the same side of the IC.

## 4. How do I determine the logic gate function of an IC?

The logic gate function of an IC can be determined by looking at the datasheet or by analyzing the circuitry of the IC. The datasheet will usually specify the type of logic gate used in the IC, such as AND, OR, NOT, etc. Additionally, analyzing the circuitry can help determine the function of the IC.

## 5. Can I use an IC with a different pin numbering scheme?

It is generally recommended to use ICs with the standard pin numbering scheme, as using a different scheme can cause confusion and potential errors in the circuit. However, if necessary, it is possible to use an IC with a different pin numbering scheme as long as the datasheet is carefully consulted to ensure the correct pins are connected.

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