Electrical – How to convert 9 bit binary to BCD for 3 Seven Segment Displays

7segmentdisplaydigital-logic

I have been learning logic gates and binary so I made an 8-bit addition and subtraction calculator. When I add or subtract, the output is 9 LED's in regular binary. I have researched ways to convert Binary into BCD to be displayed to a seven segment display using a 7447 IC. I have checked other posts on Stack exchange which I found one but it didn't really answer my question. So the question is: Is there a simple way or Ic chip that I can use to convert 9 bits into BCD without worrying about the negative numbers? I do not want to use a microcontroller so I can do everything without programming. I have also heard something about using ROM which I don't know how to use or code with Assembly but I am still interested in that. I am not experienced at all with those sort of things. Any suggestions would be very most welcome.

Best Answer

The modern technique would be to use a microcontroller to perform the conversion. Of course, you'd need one with (nominally) 20 bits of IO - 9 in and 11 out. (hint - what is the maximum value of 9 bits binary). You can get away with fewer IO lines if you add external circuitry: multiplexers on the input and latches on the output.

The old-school way is to use dedicated ICs, specifically the 74185. Of course, you'll need 6 of them, they're no longer made (although you can find them on eBay) and they need a lot of power, but it's doable.

The intermediate technique is to use a couple of PROMs. A couple of 2716s will do you, but you'll have to do your own programming. They're cheap enough although they take up some board space. This is the approach I'd use, but you can make your own choice.