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This is the simulation I did in Proteus:

This is the simulation that I did in Proteus.

The BCD adder will work for ABCDE=00010,00111,01000,01101. The LED connected to the Cout pin doesn't glow for any combination of bits. I tried connecting a resistor too in series with the LED, but it still doesn't glow. Also, the result is displayed in the 7 segment display till 9; after that, it shows some weird shapes and lines. Is there any way to resolve these issues?

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  • \$\begingroup\$ Are you sure to have connected the 2x4 parallel inputs correctly. S1 and S2 are defined by A1, B1, A2, B2. Not by A1,2,3,4. S3 and S4 are defined by A3, B3, A4, B4. Not by B1,2,3,4. Maybe this is why it results in a carry out always equal to zero. \$\endgroup\$
    – Fredled
    Nov 4, 2023 at 22:02

3 Answers 3

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This data sheet for a similar IC shows pin C0 as an input ("Carry Input"), and pin C4 as an output ("Carry Output"). From your diagram, it looks like you have them swapped. Be sure to check whatever documentation you have available (Proteus, datasheet, etc.).

Try to connect the LED to C4 if you want the carry-out pin to drive the LED.

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The 74LS47 datasheet will show the 7-segment patterns it displays for inputs 10 - 15.

I think some 7 segment decoders will make a reasonable attempt to show A, B, C, D, E, F for counts 10 - 15, but the 74xx47 doesn't.

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As Toolic said in his answer, The Carry Out pin should be C4, not C0.

The 7-segment decoder is only able to display numbers and some letters like C, A, H and symbols which can be composed with 7 segments. Anything else will look like modern Korean or something. See ASCI to Binary table to see what binary combination can give.

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  • \$\begingroup\$ U3 : 8 to 4 Binary counter. \$\endgroup\$
    – Fredled
    Nov 3, 2023 at 22:35
  • \$\begingroup\$ greybeard Thanks for correcting me. So it was not a binary counter as I thought before but a full adder. Nevertheless the Carry-Out pin is always carrying out signal at the end of a counting or sequencing process. In this case, I guess, when the 8th parallel input is high. (I will check later the 7483 datasheet) \$\endgroup\$
    – Fredled
    Nov 4, 2023 at 11:33

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