george mason university ece 448 – fpga and asic design with vhdl fpga devices & fpga design...

George Mason UniversityECE 448 – FPGA and ASIC Design with VHDL

FPGA Devices& FPGA Design Flow

ECE 448Lecture 5

2ECE 448 – FPGA and ASIC Design with VHDL

Block R

AM

s

Block R

AM

s

ConfigurableLogicBlocks

I/OBlocks

What is an FPGA?

BlockRAMs

3

Modern FPGARAM blocks

Multipliers

Logic blocks

Graphics based on The Design Warrior’s Guide to FPGAsDevices, Tools, and Flows. ISBN 0750676043

Copyright © 2004 Mentor Graphics Corp. (www.mentor.com)

Multipliers/DSP units

RAM blocks

Logic resources

(#Logic resources, #Multipliers/DSP units, #RAM_blocks)


Major FPGA Vendors

SRAM-based FPGAs• Xilinx, Inc.• Altera Corp.• Lattice Semiconductor• Atmel

Flash & antifuse FPGAs• Actel Corp. (Microsemi SoC Products Group)• Quick Logic Corp.

~ 51% of the market

~ 34% of the market~ 85%


Xilinx

Primary products: FPGAs and the associated CAD software

Main headquarters in San Jose, CA Fabless* Semiconductor and Software Company

UMC (Taiwan) {*Xilinx acquired an equity stake in UMC in 1996} Seiko Epson (Japan) TSMC (Taiwan) Samsung (Korea)

Programmable Logic Devices ISE Alliance and Foundation

Series Design Software

Technology Low-cost High-performance

220 nm Virtex180 nm Spartan II,

Spartan IIE

120/150 nm Virtex II, Virtex II Pro

90 nm Spartan 3 Virtex 465 nm Virtex 545 nm Spartan 640 nm Virtex 628 nm Artix 7 Virtex 7

Xilinx FPGA Families


Spartan 6 FPGA Family


CLB Structure


Programmableinterconnect

Programmablelogic blocks

The Design Warrior’s Guide to FPGAsDevices, Tools, and Flows. ISBN 0750676043


General structure of an FPGA


Xilinx Spartan 6 CLB


Row & Column Relationship Between CLBs & Slices


Three Different Types of Slices

50% 25% 25%


Slice X

14

16-bit SR

16 x 1 RAM

4-input LUT



Xilinx Multipurpose LUT (MLUT)

64 x 1 ROM

(logic)

64 x 1 RAM

32-bit SR


4-input LUT (Look-Up Table) in the Basic ROM Mode

• Look-Up tables are primary elements for logic implementation

• Each LUT can implement any function of 4 inputs

x1 x2 x3 x4

y

x1 x2

y

LUT

x1x2x3x4

y

0x1

0x2 x3 x4

0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

y0100010101001100

0x1

0x2 x3 x4

0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

y1111111111110000

x1 x2 x3 x4

y

x1 x2 x3 x4

y

x1 x2

y

x1 x2

y

LUT

x1x2x3x4

y

0x1

0x2 x3 x4

0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

y0100010101001100

0x1

0x2 x3 x4

0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

y0100010101001100

0x1

0x2 x3 x4

0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

y1111111111110000

0x1

0x2 x3 x4

0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

y1111111111110000


6-Input LUT of Spartan 6


Reset and Set Configurations

• No set or reset• Synchronous set• Synchronous reset• Asynchronous set (preset)• Asynchronous reset (clear)


MLUT as a 32-bit Shift Register (SRL32)


Input/Output Blocks(IOBs)


Basic I/O Block Structure

DEC

Q

SR

DEC

Q

SR

DEC

Q

SR

Three-StateControl

Output Path

Input Path

Three-State

Output

Clock

Set/Reset

Direct Input

Registered Input

FF Enable

FF Enable

FF Enable


IOB Functionality

• IOB provides interface between the package pins and CLBs

• Each IOB can work as uni- or bi-directional I/O

• Outputs can be forced into High Impedance• Inputs and outputs can be registered

• advised for high-performance I/O• Inputs can be delayed


Clock Management


Clock signal fromoutside world

Clocktree

Flip-flops

Special clockpin and pad

A simple clock tree






Daughter clocksused to drive

internal clock treesor output pins

ClockManager

etc.



Clock Manager


Ideal clock signal

1 2 3 4

Real clock signal with jitter

Cycle 1

Cycle 2

Cycle 3

Cycle 4

Superimposed cycles



Jitter



with jitter


“Clean” daughterclocks used to driveinternal clock trees

or output pins

ClockManager

etc.



Removing Jitter


1.0 x original clock frequency

2.0 x original clock frequency

.5 x original clock frequency



Frequency Synthesis


Figure 4-20

0o Phase shifted

90o Phase shifted

180o Phase shifted

270o Phase shifted



Phase shifting


DCM – Digital Clock Manager

PLL - Phase Locked Loop

Clock Management Tiles


Spartan-6 Family Attributes


Spartan-6 FPGA Family Members


FPGA device present on the Digilent Nexys 3 board

XC6SLX16-CSG324C

Spartan 6family

Size324 pins

Package type(Ball Chip-Scale)

Commercialtemperature range

0° C – 85° C

LogicOptimized

George Mason University

FPGA Design Flow

FPGA Design process (1)Design and implement a simple unit permitting to speed up encryption with RC5-similar cipher with fixed key set on 8031 microcontroller. Unlike in the experiment 5, this time your unit has to be able to perform an encryption algorithm by itself, executing 32 rounds…..

Library IEEE;use ieee.std_logic_1164.all;use ieee.std_logic_unsigned.all;

entity RC5_core is port( clock, reset, encr_decr: in std_logic; data_input: in std_logic_vector(31 downto 0); data_output: out std_logic_vector(31 downto 0); out_full: in std_logic; key_input: in std_logic_vector(31 downto 0); key_read: out std_logic; );end AES_core;

Specification / Pseudocode

VHDL description (Your Source Files)

Functional simulation

Post-synthesis simulationSynthesis

On-paper hardware design (Block diagram & ASM chart)

FPGA Design process (2)

Implementation

Configuration

Timing simulation

On chip testing

37

Tools used in FPGA Design Flow

Xilinx XSTXilinx XST

DesignDesign

SynthesisSynthesis

ImplementationImplementationXilinx ISEXilinx ISE

VHDL code

Netlist

Bitstream

Synplify PremierSynplify Premier

Functionally verified

VHDL code


Synthesis

39

Synthesis Tools

… and others

Synplify PremierXilinx XST

40

architecture MLU_DATAFLOW of MLU is

signal A1:STD_LOGIC;signal B1:STD_LOGIC;signal Y1:STD_LOGIC;signal MUX_0, MUX_1, MUX_2, MUX_3: STD_LOGIC;

beginA1<=A when (NEG_A='0') else

not A;B1<=B when (NEG_B='0') else

not B;Y<=Y1 when (NEG_Y='0') else

not Y1;

MUX_0<=A1 and B1;MUX_1<=A1 or B1;MUX_2<=A1 xor B1;MUX_3<=A1 xnor B1;

with (L1 & L0) selectY1<=MUX_0 when "00",

MUX_1 when "01",MUX_2 when "10",MUX_3 when others;

end MLU_DATAFLOW;

VHDL description Circuit netlist

Logic Synthesis

41

Circuit netlist (RTL view)

42

Mapping

LUT2

LUT3

LUT4

LUT5

LUT1FF1

FF2

LUT0

43

Xilinx XST Inputs/Outputs

44

Xilinx XST Inputs

• RTL VHDL and/or Verilog files• Constraints – XCF

Xilinx constraints file in which you can specify

synthesis, timing, and specific implementation

constraints that can be propagated to the NGC file.• Core files

These files can be in either NGC or EDIF format.

XST does not modify cores. It uses them to inform

area and timing optimization surrounding the cores.

45

Xilinx XST Outputs• NGC

Netlist file with constraint information• NGR

This is a schematic representation of the pre-optimized

design shown at the Register Transfer Level (RTL).

This representation is in terms of generic symbols,

such as adders, multipliers, counters, AND gates, and

OR gates, and is generated after the HDL synthesis phase

of the synthesis process.• LOG

This report contains the results from the synthesis run,

including area and timing estimation.

RTL view in Synplify Premier

incrementercomparator

General logic structures can be recognized in RTL view

MUX

Crossprobing between RTL view and code

Each port, net or block can be chosen by mouse click from the browser or directly from the RTL View

By double-clicking on the element its source code can be seen:

Reverse crossprobing is also possible: if section of code is marked, appropriate element of RTL View is marked too:

Technology View in Synplify Pro

Technology view is a mapped RTL view. It can be seen by pressing button or by double-click on “.srm” fileAs in case of “RTL View”, buttons can be used here

Two additional buttons are enabled: - show critical path - open timing analyst

Technology view is presented using device primitivesPorts, nets and

blocks browser

Pay attention: technology view is usually large and presented on number of sheets

Viewing critical path Critical path can be viewed by pressing on

Delay values are written near each component of the path


Implementation

51

Implementation

• After synthesis the entire implementation process is performed by FPGA vendor tools

52

Implementation

53

Translation

Translation

UCF

NGD Native Generic Database file

Constraint Editoror Text Editor

User Constraint File

Circuit Netlist

Timing Constraints

Synthesis

54

Mapping

LUT2

LUT3

LUT4

LUT5

LUT1FF1

FF2

LUT0

55

PlacingCLB SLICES

FPGA

56

Routing

Programmable Connections

FPGA

57

Configuration

• Once a design is implemented, you must create a file that the FPGA can understand• This file is called a bit stream: a BIT file (.bit extension)

• The BIT file can be downloaded directly to the FPGA, or can be converted into a PROM file which stores the programming information

Two main stages of the FPGA Design Flow

Synthesis

Technologyindependent

Technologydependent

Implementation

RTLSynthesis

Map Place & Route Configure

- Code analysis- Derivation of main logic constructions- Technology

independent optimization

- Creation of “RTL View”

- Mapping of extracted logic structures to device primitives

- Technology dependent optimization

- Application of “synthesis constraints”

- Netlist generation- Creation of “Technology

View”

- Placement of generated netlist onto the device

- Choosing best interconnect structure for the placed design

- Application of “physical constraints”

- Bitstream generation

- Burning device

george mason university ece 448 – fpga and asic design with vhdl fpga devices & fpga design...

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