VHDL Design of VHDL Design of Multifunctional RISC Multifunctional RISC Processor on FPGAProcessor on FPGA

A.Girish Pawan KumarV.Raghavendran

S.SudarsanV.Swaminathan

VLSI Basics

VLSI-Very large scale integrated circuit. Electronic system with integrated dedicated components. Semi custom and full custom. Design styles-ASIC,PLD,CPLD,FPGA,system on chip. FPGA-RAM based devices,these devices loose their

configuration when power is switched off. FPGA uses hex file for design. FPGA programming-Verilog and VHDL.

VHDL basics VHDL-Very high speed IC Hardware Description Language. Modeling of digital system. Concurrent and sequential statements. Man and machine readable specification. Simulatable source code.

Modeling Behavioral,structural,data flow.

FeaturesStrongly typed-describes from abstract to concrete level.Case insensitive.Top- down and down-top methods.Flexible design methods.

What is RISC? Computer arithmetic-logic unit. Fastest instruction execution. Instructions are of same size and execute within a

single cycle. Efficient way of completing a operation. Reduces hardware space complexity.

PropertiesSmaller number of instruction commands.Single word standard length.Large general purpose CPU registers. Less costly to design, test and manufacture.Fixed length and easy decoder format.

CISC Vs RISC

CISC Emphasis on hardware

Includes multi-clockcomplex instructions

Memory-to-memory:"LOAD" and "STORE"incorporated in instructions

Small code sizes,high cycles per second

Transistors used for storing complex instructions

RISC Emphasis on software

Single-clock,reduced instruction only

Register to register:"LOAD" and "STORE"are independent instructions

Low cycles per second,large code sizes

Spends more transistorson memory registers

Features An 8 bit processor. Designed for achieving one clock per instruction. Memory facilitates the control unit with the instructions

which in turn generates appropriate signals for rest of the processor.

Provides four to ten times better performances than existing micro controllers.

Data path

RISC ARCHITECTURE

INSTRUCTION MEMORY

INSTRUCTION DECODER

ROM5-bit Address16-bit Data

Multiple output logic circuitControl SignalsInstruction and address

REGISTER

ALU BLOCK

group of flip-flops to store 1-bit information.

both storing and retrieving data.

arithmetic and logic functions on 8-bit data.

addition, subtraction, excess 3, increment, decrement compare,logic gates, Shifting operations, complement.

Stepper Motor Control

Electromechanical DeviceStatorRotorField coils

Simulation MODELSIM software Mixed language simulator Design up and running is quick Test benches-regression test Low cost,consumes less time and good

performance. Signals in design-waveform generation.

DEMUX

D I V I D E R

CLOCK

Synthesis

Converting higher level of abstraction to lower level of abstraction

Higher level-HDL language Lower level-equivalent gate level implementation of

HDL language Xilinx synthesis technology-project navigator Project Navigator-design source files,run processes,view

output. It integrates the tools and process is designed easily.

RTL SCHEMATICS

RISC

BLOC K S

STEPPER MOTORCONTROL

Keypad and LCD interfaceRI SC

P INS

LCD AND KEYPAD

Kit Specifications INPUT: 230V,50Hz. OUTPUT: +5V DC. LCD: 16*2 display. LED:16 digital I/O indication. DIP switches:inputs and outputs. 4 x 3 Keypad CPLD,micro controller,clock provider. ADC,DAC. FPGA - XC 2S 150 ,plastic quad,208 pins,15MHZ. MICRO CONTROLLER - ATMEL 89C519,18.432MHZ. 40 I/O’s of the device are available for external use.

Spartan II Kit

Configuration SANDS FPGA DEVELOPMENT PLATFORM Software

-Configures FPGA device and checks for functionality-Transferring the hex file from the system to the kit.

Applications

Engineering and Graphic work station. Parallel processing systems. Ideal for Embedded applications (mobile phones,

digital cameras, etc).

Apple iMAC RISC inside the system

Conclusion

RISC is an evolution in computer architecture.

Emphasizes on speed and cost-effectiveness over the ease of assembly-language programming and conservation of memory.

RISC-based designs will continue to grow in speed and ability, more rapidly than CISC design.

FUTURE TRENDS

The features of RISC processor can be extended by including Program Counter, Generic Statement, Load and Store instructions. This facilitate running the program continuously, increasing the number of bits.