Displaying an 8-bit binary count on 3x 7-segment displays

[JohnSym]

I'm fairly new at all this, and feeling a little out of my depth. I need to simulate a circuit that takes a 8-bit binary signal (counts to 255) and display the decimal count on 3x 7-segment displays. Binary-to-BCD is the only part of this project i'm struggling with.

I'll simplify my situation so i can ask my question...

Bringing it back down to 4-bits so i can understand how it works, i run the 4-bit binary through a 4511 and it counts 0-9 then blanks for the other 6 counts.

I can display 0-9 (repeating properly) on a 74191 if I set the LOAD to HIGH (ignoring the inputs). But this is no good, because i need it to respond correctly to the given inputs. And even then, it needs to cascade to the second device.

So what i'm asking is this... how do i cascade these devices (and also, what devices?) so that the 7 segment displays show the decimal version of the binary signal??

Hoping someone can point me in the right direction.

[Miguel_V]

Hello,

You could try looking ta the large amount of sample files that ship wit Multisim. You'll find plenty examples (counters, adc's etc) which you can use to try to simulate your circuit. The blue folder next to the regular load folder is a direct link to the folder containing all the samples. Try looking in the educational section.

Kind regards,

[JohnSym]

Thanks; those sample files have been great in getting me this far, but as far as BCD displays go, they only seem to give examples of simple counting (with the inputs tied high)... they dont actually seem to count anything.

That part is fairly straightforward; they simply count to 1001 (9), reset  and start again. But I need to be able to put any given 8-bit number into the system, and have it return the equivalent value on the display. So rather than disregarding any 4-bit number above 1001, i would need it to pass on that 'remainder' to the next device, and have it pick up the count.

I cant find anything in the sample files that do that. Unless i've seen it and haven't understood what i was looking at 😞

[JohnSym]

I think i understand what i'm supposed to do, but have no idea how to do it.

The first device (i'm not even sure what device) recieves a binary signal that counts up and displays on the first 7-sgment display (indicating 'ones' unit). It operates normally until it hits 1010 (10). Then it needs to (a) reset and count again, and (b) send a carry of '1' to the next device (that presumably gets added to it's own binary count). When the binary count of the first device gets to 1011 (11), it sends a carry of '2' and so on until it reaches 1111 (15) and sends a carry of '6'. Then starts again.

The second device adds these carries from the first device to it's own binary count (accomplished with a series of adders?), and then behaves in much the same manner, sending the result to the second 7-segment display (indicating 'tens' units). It's own carries get sent to a decoder that drive the third 7-segment display (indicating 'hundreds' unit). 

Is my reasoning ok? Is this the best way or is there a better? Any suggestions on the best devices to do this?

Any help is appreciated. The guidance from our lecturer has been non-existant.

[Miguel_V]

Hello,

Well, I can tell you there is a lot of examples out there (in forums, in the wob, in youtube) and you can find a lot of ideas on how to do a project. As for a BCD, you should be able to find one in the TTL group. A 7447 is a 4 bit input 7 segment display output chip that you can use to power a single counter. You can stack these to eventually have a 2-3 display counter. Also, there are a few physics and electrenic forums designed for help in this topic, especially when it comes to design and homework. Good luck with your project.

Kind regards,