Computer Organization and Assembly Language

4 bit 2s Complement Multiplier

INPUT A: 4 bit 2s Complement number INPUT B: 4 bit 2s Complement number OUTPUT: the product of A x B represented as a 8 bit 2s Complement number

You are only allowed to use the basic gates: NOT, AND, OR, XOR. You may however, use these basic gates to build your own custom circuits (i.e. Adder). You are NOT ALLOWED to use Logisims built in circuits. Each custom circuit is to be implemented as a sub-circuit as discussed in class.

PART 1: Build a 4 bit controlled 2s Complement Inverter

PART 2: Build a 8 bit controlled 2s Complement Inverter

PART 3: Build a 4 Bit UNSIGNED Multiplier

PART 4: Using the custom circuits you built in Parts 1-3, built a 4 bit 2s Complement multiplier that uses the inversion method discussed in class.

HINTS: INVERSION METHOD:

1) If input A is negative, invert it. If input A is positive, leave it alone. 2) If input B is negative, invert it. If input B is positive, leave it alone. 3) Multiply A and B. 4) If both A and B originally had the same sign (both positive or both negative), do nothing. 5) If A and B originally had different signs (one was positive, the other negative), invert the product.