Half Subtractor

The circuit performs the function of subtracting two binary digits. Using the two input bits the circuit produces the difference (DIFh) and borrow output (BOh). DIFh will be set if either, but not both, of the input variables is 1. BOh will be set when minuend (MD) is low and subtrahend (SD) is high. A two-input Exclusive OR (XOR) gate and a two-input AND gate preceded by an inverter to complement the MD input were used to generate DIFh and BOh respectively. Variables / Signal Names: MD = Minuend SD = Subtrahend DIFh = (Half Subtractor) Difference BOh = (Half Subtractor) Borrow Output Boolean Equations: DIFh = MD (+) SD BOh = MD' · SD