Simple 4:2 carry-save-adder and 4:2 carry save add method

摘要

Provided are a simplified 4:2 carry save adder (CSA) cell and a 4:2 carry save adding method. The 4:2 CSA cell is formed of an odd detector and first through sixth switches through logic optimization. The odd detector generates an XOR of the first through fourth input signals, outputs the XOR as an odd signal, generates an XOR of the first and second input signals, and outputs the XOR as a first XOR signal. The first switch outputs the third input signal as a carry output signal in response to the first XOR signal. The second switch outputs the first input signal as the carry output signal in response to an inverted first XOR signal. The third switch outputs the carry input signal as a carry signal in response to the odd signal. The fourth switch outputs the fourth input signal as the carry signal in response to an inverted odd signal. The fifth switch outputs an inverted carry input signal as a sum signal in response to the odd signal. The sixth switch outputs the carry input signal as the sum signal in response to the inverted odd signal.