4 Bit Serial Adder Block Diagram. After that output is used as carry for next significant bits. We already know that two numbers a minuend and b subtrahend can be subtracted using 2s complement method where a b a 2s complement of b a 1s complement of b 1 thus 4 bit binary numbers a and b can subtract as and the logic circuit for the same can be drawn as parallel adder subtractor using a single circuit can be also designed using a mod bit m where mod bit m.
A full adder adds two 1 bits and a carry to give an output. The sum bit from the output of the full adder can be transferred into a third shift register. After that output is used as carry for next significant bits.
Hence its c in has been permanently made 0.
Block diagram and logic circuit diagram of a 4 bit binary adder can be given as 4 bit binary subtractor. So in order to add two 4 bit binary numbers we will need to use 4 full adders. The rest of the connections are exactly same as those of n bit parallel adder is shown in fig. Shift register is a group of flip flops used to store multiple bits of data.
