Digital Circuits and Systems - Circuits i Sistemes Digitals (CSD) - EETAC


	4-bit serial multiplier (add & shift algorithm)	P8

Dedicated processor (datapath + control unit)

1. Specifications

Note: review, update: This project follows former CSD naming conventions and styles and is not yet updated. It has to be rewritten contextualising this application again as a dedicated processor. Comparison of a hardware combinational multiplier and this serial multiplier.

Cooperative groups will have to specify, plan, develop, simulate, implement and prototype a complex application such as serial multiplier.

2- BCD digits to display the result (Board HWD-LC4128V, Lattice CPLD chip).
A set of 8 switches to input A and B operands, or alternatively a matrix keyboard.
20 kHz clock synchronous system.
Pushbuttons to start operation, visualise results, and a LED for signalling the end of operation.
Serial add-and-shift algorithm.

Fig. 1 shows the symbol, the top level scheamatic to adapt the design to HWD-LC4128V prototyping board and the pin assigment for inputs and outputs (switches, buttons, LEDs and 7-segment digits). This is the visio of the symbol.

Class notes (pdf1) (pdf2) (pdf3) (pdf4) (pdf5) (pdf6) on problem discussion.

Fig. 1. Symbol, top schematic adaptation and prototyping board.

2. Plan C2 based on a dedicated processor

Devising a plan:

The project much be finished before the due date.
As discussed in previous section, the idea is organise the problem top-down, and then go back bottom-up.
Each cooperative group will be in charge of the design of a multipliers component.
The VHDL programming style for the components will be exemplified through the design of the data register.
Some important blocks, like the multipliers control unit will be solved by every student individually.
Fig 2: The top architecture [G7].

Fig. 2. Architecture of a dedicated processor.

3. Development

Top architecture and components.

Fig. 3. Complete planning using a dedicated processor architecture.

Fig 4: Internal architecture of the unsigned multiplier as a dedicated processor.

Fig 5: Structural RTL level architecture of the datapath and control unit.

Each group designs their component using the typical PLD design flow (symbol, specifications (truth table for a CC, state diagram or/and timing diagram for a SS), ActiveHDL project, functional simulation using a ispLEVER-generated test bench, RTL schematic, gate-level simulation of the synthesised circuit, analysis of used resource used, and reporting.

Fig. 6. State diagram of the FSM control unit.

All the VHDL files.

Number of VHDL files involved	Block to be designed and some remarks	Entity name (VHD) / top design	Components (hierarchy level 1)	Components (hierarchy level 2)	Components (hierarchy level 3)
21	Multiplier (the top entity)	multiplier.vhd	(This file is the structure of the top entity, as shown above in Fig 1)
8	The 4x4 unsigned serial multiplier	unsigned_4bit_multiplier.vhd	Datapath.vhd	Data_Reg_8bit.vhd Shift_Data_Reg_8bits.vhd Shift_Data_Reg_4bits.vhd
			Datapath.vhd	Adder_8bit.vhd	One_bit_adder.vhd
			control_unit_multiplier.vhd
3	5 s timer. This is a complex digital system in itself: a datapath, in this case a counter, controlled by a FSM	timer.vhd	counter.vhd control_unit_timer.vhd
1	4MUX4 (Chapter 1)	Quad_MUX4.vhd
2	Code converter from binary to BCD (Units, tens and Hundreds) (Chapter 1, see a truth table and a block diagram for the 74185 chip)	Bin_BCD_converter_8bit.vhd	Bin_BCD_type74185.vhd
1	Binary to 7 segment decoder with "H" symbol.	BCD_7seg.vhd
5	Clock divider	OSC_FREQ_DIV.vhd	Freq_Div_100.vhd Freq_Div_50.vhd Freq_Div_2.vhd T_Flip_Flop.vhd

4. Test (functional)

Design the Active-HDL test bench for the top Multiplier project.

Functional simulation.

5. Test (gate-level)

Gate-level simulation.

6. Prototyping

Demonstrate how the board works for real as a laboratory prototype.

Add other features, link the project with other or learn on how th implement multipliers using different algorithms

7. Report

Example of report for this project (Author: Angélica Rodríguez Sánchez).

Other questions: How to multiply 8x8 bit numbers using an 4x4 multiplier?

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4-bit serial multiplier (add & shift algorithm)