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Best adder with subtraction functionality

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supamaka

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Hello,
I am currently involved in doing a project in VLSI, one of the functionalities in it needs me to do a 32 bit adder which needs to implement a subtraction functionality too.

I want advice from members as to what could be the best adder to choose for this project, my goal here is to maximise speed as our project is on speed optimisation. I have decided upon Double pass transistor logic for the adder circuitry, could anyone please tell me if this is the best for the project or is there anything better.

Thanks,
Andy.
 

a block carry look ahead adder would be an optimised one with carry and the sum being generated from pass transisitor logic..
in block carry look ahead adder u combine M bits implement it in look ahead adder fashion ..
ie combine 4 bits of 32 hence 8 blocks
 

Hi
parallel prefix adders gives better speed as per synopsys. regarding substraction u can give the inputs complimented and carry as 1 if u r using 2's complement arith.
 

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