8-bit binary adder using two 7483s and 7seg displays

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Joined Feb 21, 2007
For my digital electronics class, we've been presented with a challenge that not even the teacher knows how to do. The easy part is adding the two 8-bit binary numbers by using the carry out of one and the carry in of the other. The result is a 9-bit number in binary (currently being displayed with LEDs). The next step is to display each 8-bit number (which is being added) with 7-segment displays (displaying the decimal equivalent) and to display the 9-bit sum using 7-segment displays.

We input the 8-bit numbers with 8 switches (representing high or low) per number to represent each bit.

For example, using our switches, we add 10101010 and 00001110 for a sum of 010110000. We then need to display each one of those numbers with a seven segment display. We have no idea how to (efficiently) do this. Are there any chips or demuxes or anything that we could use to convert the 8 and 9 bit binary into seven segment displays? We would need 3 displays per number, since it can be up to three digits in base10 form.


Joined Apr 20, 2004
Without using a microprocessor to accomplish what would then be a trivial task, you'll need a bit of extra logic. You might load the sum of the adders into a pait of parallel-load counters, plus togling a flip=flop for the carry bit.

Count that counter string down to zero, while counting up a decimal counter string. Have 7 segment drivers run off the BCD outputs of the decimal counter string.

You will need extra logic to latch the original binary data into the binary counter string, a clock source, and logic to stop the binary counter decrement at zero.
How did you tackle this since i have a similar problem for my project. most prob it's a pic i'll have to use but i can't afford to program the stuff since the number display is rather a 'comodity' which i have to do without for the moment. how did you solve the prob please?