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how to build a non-signed subtractor efficiently

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JesseKing

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subtract a positive number from another, and use a sign extension format to represent the result, the msb is the sign bit.

For example
0011-0010=0001
0010-0011=1001

Can this subtractor be implemented efficiently as a complementry subtractor?

Regards!
 

eda_wiz

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JesseKing said:
subtract a positive number from another, and use a sign extension format to represent the result, the msb is the sign bit.

For example
0011-0010=0001
0010-0011=1001

Can this subtractor be implemented efficiently as a complementry subtractor?

Regards!

assuming the inputs are 4 bit unsigned
you need five bit represent signed output.
 

JesseKing

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whizkid said:
assuming the inputs are 4 bit unsigned
you need five bit represent signed output.

i know, the function is not hard to understand and it's easy just to build it with a comparator and a traditional complementary adder.

what I really want to know is how to implement it efficiently.

any advice?
 

linuxluo

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hi,
the best way is to use design ware from syn@psys
 

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