Comp Sci Why Does My 19-bit Adder Using 74LS283 ICs Show Incorrect Results in Proteus?

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SUMMARY

The forum discussion addresses a problem with a 19-bit adder implemented using the 74LS283 Integrated Circuit (IC) in Proteus, where incorrect results were produced due to grounding the S3 output. Users clarified that grounding any output, particularly S3, is incorrect as it can lead to energy wastage and potential chip damage. The correct approach involves allowing the carry output (C4) to float while connecting S4 to S19 to obtain the correct 20-bit result. Following this guidance resolved the user's issue.

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Lord Doppler
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Homework Statement
Make a 19 bits adder
Relevant Equations
Boolean Algebra, Logic
Hello, I'm doing a 19 bit adder in Proteus with the 74LS283 IC and I have a problem, I'm adding 1110111000110011010 (487834) with 0001110110001100111 (60519) which the result is 10000101111000000001 (548353) and Proteus doesn't the correct result. It is not taking into account the carry, someone can help me?

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Why are you grounding S3 in the most significant digit? One should not ground any output, and you need that output to get your 20 bit result.

The carry bits seem to be getting through just fine.
 
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Halc said:
Why are you grounding S3 in the most significant digit? One should not ground any output, and you need that output to get your 20 bit result.

The carry bits seem to be getting through just fine.
Because I need add 19 bits and not 20 bits I grounded S3 in the most significant digit, it's correct? I need add 19 bits and the carry
 
It is not correct to ground any output. You let it float if you don't care about the 20th bit. Grounding an output wastes energy at best, and burns out your chip at worst. I don't think LS technology will burn out since the fan-out implies an obvious current limit.

In that case, the 1st 19 bits of the the answer you got (shown in the bottom horizontal line) is correct. But you show 20 bits of answer, the last one being taken from the wrong line.

Lord Doppler said:
I need add 19 bits and the carry
The carry is the 21st bit. If you want 20 bits of output, s4 is that 20th bit, and it should be c4 that you let float. c4 is always going to be low anyway in the last chip.

I see you are calling the c4 line 's19', but it is actually 's20'. s19 is the s4 line, which you've grounded.
 
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Halc said:
It is not correct to ground any output. You let it float if you don't care about the 20th bit. Grounding an output wastes energy at best, and burns out your chip at worst. I don't think LS technology will burn out since the fan-out implies an obvious current limit.

In that case, the 1st 19 bits of the the answer you got (shown in the bottom horizontal line) is correct. But you show 20 bits of answer, the last one being taken from the wrong line.

The carry is the 21st bit. If you want 20 bits of output, s4 is that 20th bit, and it should be c4 that you let float. c4 is always going to be low anyway in the last chip.

I see you are calling the c4 line 's19', but it is actually 's20'. s19 is the s4 line, which you've grounded.
Oh ok, then I will never ground an output, I didn't know. I tried float the C4 in the last chip and connect S4 to S19 for obtain the 20 bits in the output as you said and it works! Thanks
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