I've been having trouble with this 8 bit adder/subtractor. It's "built up" from a 1 bit full adder, then a 4 bit adder/subtractor and then, finally, into a full 8 bit adder/subtracter.
The 1 bit full adder works perfectly.
The 4 bit adder/subtracter, built up from the 1 bit full adder, works perfectly.
The final, 8 bit adder/subtractor, is where my problem lies and I have beat my head against the wall until the dents are now noticeable (in both my head AND the wall).
The 'fix' has GOT to be simple but it sure hasn't popped into my head...and I've tried so many iterations to resolve it I've lost track of what I've done and haven't done!
I'm pretty certain the problem lies in how the COUT and CIN values are being passed from the 1st 4 bit adder/subtractor iteration to the 2nd...but danged if I can figure out what I've done wrong!
Can ANYBODY tell me what's wrong with the final 8 bit adder/subtractor? PLEASE (and thank-you!)
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jrosengarden
To All:
I've been having trouble with this 8 bit adder/subtractor. It's "built up" from a 1 bit full adder, then a 4 bit adder/subtractor and then, finally, into a full 8 bit adder/subtracter.
The 1 bit full adder works perfectly.
The 4 bit adder/subtracter, built up from the 1 bit full adder, works perfectly.
The final, 8 bit adder/subtractor, is where my problem lies and I have beat my head against the wall until the dents are now noticeable (in both my head AND the wall).
The 'fix' has GOT to be simple but it sure hasn't popped into my head...and I've tried so many iterations to resolve it I've lost track of what I've done and haven't done!
I'm pretty certain the problem lies in how the COUT and CIN values are being passed from the 1st 4 bit adder/subtractor iteration to the 2nd...but danged if I can figure out what I've done wrong!
Can ANYBODY tell me what's wrong with the final 8 bit adder/subtractor? PLEASE (and thank-you!)
addsub_8bit_cascade4.txt
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