Greetings everyone!

I have to do a school project in Proteus ISIS software, and the task is to display 8 bits on three seven segment displays. I can only use basic logic gates (AND, OR, XOR, etc.). I'm desperate to find a solution. I would be very grateful for any helpful tip.

 

Greetings everyone!

I have to do a school project in Proteus ISIS software, and the task is to display 8 bits on three seven segment displays. I can only use basic logic gates (AND, OR, XOR, etc.). I'm desperate to find a solution. I would be very grateful for any helpful tip.

Well, 8-bits can yield 2 to the eighth (2^8) combinations to yield values (in binary) from 0 to 255.

What have you done so far? We don't usually do things for posters, we help them when they run into problems.

 

I'm trying it with full adders, but I don't know how to wire them properly. I can use the 7447 decoder for the displays.

 

I'm trying it with full adders, but I don't know how to wire them properly. I can use the 7447 decoder for the displays.

Does it have to count and display pulses or just display a value entered with switches?

 

No, it doesn't have to count. Just to display it using switches as you say sir.

 

Read through this thread for starters.

https://forum.allaboutcircuits.com/threads/binary-adder-with-7-seg-display.59553/#post-400823

 

Thank you very much sir!

 

Greetings everyone!

Welcome to AAC!

I have to do a school project in Proteus ISIS software, and the task is to display 8 bits on three seven segment displays. I can only use basic logic gates (AND, OR, XOR, etc.).

Can you post the entire text of the problem? A binary to decimal converter is more complex than a BCD or octal converter.

I'm desperate to find a solution. I would be very grateful for any helpful tip.

It's good that you're looking for tips because AAC members are discouraged from simply providing solutions to homework.

By homework, we mean any school work for which you will be graded.

 

I've found this video on youtube:

This guy uses 2x4 bit full adders and displaying the result on 2x7 segment displays. The problem with this is that it only displays numbers from 0 to 15 (2^4), while I need to display numbers from 0 to 255 as mentioned above. I don't know what should I do to make it display from 0 to 255. My first idea would be to add 2 more 4 bit full adders, but I don't know how to wire them up properly.

 

My first idea would be to add 2 more 4 bit full adders, but I don't know how to wire them up properly.

Why do you want to use adders when you're supposed to design a decoder?

 

I can use the 7447 decoder, all I need is to add the 8 bit with each other and display it on 3x7 segment

 

all I need is to add the 8 bit with each other

What do you mean add?
Do you have more than one 8-bit number?

Converting binary to BCD is not as easy as it might appear.
Here's an old thread on that.
One of the simpler ways may be to use an 8-bit binary down-counter along with a 3-digit BCD up-counter.

 

I'm trying it with full adders, but I don't know how to wire them properly. I can use the 7447 decoder for the displays.

Are you implementing your adders using basic logic gates? It's fine if you aren't because, once you have it working with adders, you should be able to replace them with gate-level implementations.

Or can you use adders? You first said only basic logic gates and then later said that you could use 7447 decoders. So, please, tell use what the problem actually states, so that we don't go steering you down either a road that is too primitive or one that is too high level for what the constraints actually are.

 

I've found this video on youtube:

This guy uses 2x4 bit full adders and displaying the result on 2x7 segment displays. The problem with this is that it only displays numbers from 0 to 15 (2^4), while I need to display numbers from 0 to 255 as mentioned above. I don't know what should I do to make it display from 0 to 255. My first idea would be to add 2 more 4 bit full adders, but I don't know how to wire them up properly.

Have to taken the time to understand how that guy's circuit works? Once you get to that point, then you can take what you've learned and apply it to this related, but larger, problem.

 

I don't see how a BCD adder (which is what the youtube video states it's making) can be used to go from binary to BCD.

 

I can use the 7447 decoder, all I need is to add the 8 bit with each other and display it on 3x7 segment

Yes the 7447 is a decoder that converts BCD to 7 segment format.

But you need another decoder that would decode (or convert) binary to BCD so that the 7447 could use that BCD outputs to drive their BCD inputs.

Try download the datasheet of dm74185 and see how it was connected. Unfortunately the internals of the chip was not shown or else you can just copy its design.

Allen

 

Try download the datasheet of dm74185 and see how it was connected.

That reminded me of this thread from April 2017. National's version of 74185 was implemented as a look up table, but they did give an algorithm. The OP in that thread lost interest after a couple of posts. Apparently he lost interest in AAC all together because his post count stopped at 2.

We need the OP to clarify requirements. If the input is 8 bits of BCD, the solution is straightforward. If the input is binary, that's a more difficult problem.

Then there's the issue of what components are allowed. Initially it was just "basic logic gates" which later appeared to include 7447. The OP is exercising selective reading because I asked for the complete text of the problem and, two posts later by the OP, we still don't have it.

 

Yes, this binary to BCD topic has appeared many times in AAC as well as ETO forums.

But members usually suggested MCU or ROM tables methods as the hardware logic solution was too complicated to implement. So discussions were always ended without any fruitful results.

I guess it will be the same for this one.

Allen

 

The binary down-counter with a BCD up-counter is a workable, albeit somewhat complex solution to do with only basic gates available.

 

OK, if you want to try @crutschow's method, you can go ahead.

But here I would like to show you how to convert a 4 bit binary number to 2 digit BCD and show them as 2x 7-segment numbers on proteus.

Using this example you might be able to figure out how to convert an 8-bit binary to 3x 7 segment LED digits...

First generate the truth table using excel.


Based on the table, write 5 boolean expressions for D4-D0 wrt to D,C,B,A.
You can use KMap or whatever tools you have.

Put the 5 expressions on proteus and try out the sim.


Now do you think you can do an 8 bit version of this?

Allen