Laboratory 5

Aim: To design and simulate (using XILINX) and implement a 4-bit sequential multiplier.

Material needed: Protoboard, Logic template, two 74377 8-bit registers with load enable, one 74LS169A 4-bit up down counter, 74175 D-FFs, two 7483 4-bit parallel adders, SPDT switches, DIP switches, a set of resistors (0.25W, 1k ohms and 0.25W, 330 ohms), square wave generator, LEDs, 7-segment displays, AND, OR, NAND gates, and wires for Protoboard.

Problem: your goal is to design and implement a sequential multiplier that takes as input two 4-bit numbers A and B and produces an 8-bit product C. The first few steps in this experiment are as follows:

1. Connect DIP switches to drive parallel load inputs to shift registers and counters.

2. Connect 7-segment displays to show the contents of each register and the counters.

3. Connect clock input to an SPDT switch.

Prelab: Design the circuit that will perform the multiplication by adding A to itself B times. In particular:

1. Load in parallel 'A' into the first of registers.

2. Load in parallel 'B' into the counter.

3. Clear the second register that holds the partial product.

4. Use a "GO" signal to start the multiplication.

5. Decrement the counter until it becomes all zero and

6. For each decrement step add 'A' to the partial sum stored in the second 8-bit register 'C'.

7. EXTRA CREDIT: obtain the "GO" signal from a push-button and use it as an input to a control unit (a Moore machine to be constructed out of D'FFs and gates) that generates the necessary signals for loading and enabling the counter and the registers.

Demo: Build the circuit and demonstrate its operation by applying different input sequences.