13-02-2013, 04:55 PM
Carry Save Adder Implementation
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INTRODUCTION
Now that we have seen that the carry save adder trees are most efficiently implemented by putting together the (3,2) blocks, we must still address the issue of how to implement the (3,2) block (carry save adder) efficiently. Functionally, the carry save adder is identical to the full adder. The full adder is usually implemented with a reduced delay from Cin to Cout because the carry chain is the critical delay path in adders. Unfortunately, there is no single carry chain in the carry save adder trees in multipliers. Thus, it does not pay to make the delay shorter for one input by sacrificing delay on other inputs for carry save adders. Instead, carry save adders are normally implemented by treating the 3 inputs equally and trying to minimize delay from each input to the outputs.