Introduction to Programmable Logic Devices

Introduction toProgrammable Logic Devices

John Coughlan

STFC Technology Department

Detector & Electronics Division

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

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

Programmable Logic is a Key Underlying Technology for PP Experiments.

First-Level and High-Level Triggering

Data Transport (Networks)

Computers interacting with Hardware (Networks)

Silicon Trackers (Millions of Data Channels)

Commercial Devices. Developments driven by Industry.

Telecomms, Gaming, Aerospace, Automotive, Set-top boxes….

PPD Lectures

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CMS

CERN LHC

Particle Physics Electronics

Custom Electronics ChipsASICs ANALOGUE $$$Rad Hard, Low Power

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CMS

CERN LHC

Electronics Rooms


Trigger Systems. DAQ Systems.DIGITAL

Custom Electronics ChipsASICs ANALOGUE $$$Rad Hard, Low Power

Custom Digital Processing BoardsVME Bus Crates

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Special Dedicated Logic Functions (not possible in CPUs) Ultra Fast Trigger Systems (Trigger Algorithms) Clock Accurate

Timing Massively Parallel Data Processing (Silicon Trackers with Millions of

Channels)

Custom DesignedPrinted Circuit Boards PCBs.

CommercialProgrammable LogicDevices, FPGAs

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CMS DAQ/Trigger Architectures

CMS

“Telecoms Network” ~ 1 Tbps

Fully custom PP ASICs

CPUs Commodity PCs

Programmable LogicDIGITAL

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Lecture Outline

Programmable Logic Devices Basics Evolution

FPGA Field Programmable Gate Array Architecture

Design Flow Hardware Description Languages Design Tools

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Digital Logic

Logic Gates

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Digital Logic

Logic Gates

Transistor Switches

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Digital Logic

Logic Gates

Transistor Switches

< 40 nm ! $$$

MOORE’S LAW

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Digital Logic

Black BoxSUM of PRODUCTS

Truth Table(Look Up Table LUT)

Digital Logic Function

3 Inputs

Product AND (&)Sum OR (|)

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Digital Logic




3 Inputs


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Digital Logic




3 Inputs


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Programmable Logic Devices PLDs

Un-programmed State

SUM of PRODUCTS (Re-)Programmble Links Reconfigurable GLUE LOGIC

Logic Functions

Planes ofANDs, ORs

Inputs

Outputs

ANDs

ORs

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Un-programmed State


Logic Functions

Planes ofANDs, ORs

Inputs

Outputs

ANDs

ORs

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Un-programmed State


Logic Functions

Planes ofANDs, ORs

Inputs

Outputs

ANDs

ORs

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Un-programmed State


Logic Functions

Programmed PLD

Product Terms

Sums

Planes ofANDs, ORs

Inputs

Outputs

ANDs

ORs

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Logic Functions

Programmed PLD

Product Terms

Sums

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Logic Functions

Programmed PLD

Product Terms

Sums

x x

x x x

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Logic Functions

Programmed PLD

Product Terms

Sums

x x

x x x x

x

GLUE LOGIC

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Complex PLDs

CPLDs Programmable PLD Blocks Programmable Interconnects Electrically Erasable links

CPLD Architecture

Feedback Outputs

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Sequential Circuits Combinational Logic (Larger circuits difficult to predict) Synchronous Logic driven by a CLOCK Registers, Flip Flops (Memory)

Inputs

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Sequential Circuits

RegisterCLOCK

New Output every clock edge

Combinational Logic (Larger circuits difficult to predict) Synchronous Logic driven by a CLOCK Registers, Flip Flops (Memory)

Inputs

Intermediate

EDGES

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Sequential Circuits

RegisterCLOCK

New Output every clock edge

Shift Registers,Pipelines,Finite State Machines…

Combinational Logic (Larger circuits difficult to predict) Synchronous Logic driven by a CLOCK Registers, Flip Flops (Memory)

Clock Rate determines speed

Comb Logic Must meet Timing=> Predictable circuits

Inputs

Intermediate

EDGES

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Field Programmable Gate Arrays FPGA

Field Programmable Gate Array ‘Simple’ Programmable Logic Blocks Massive Fabric of Programmable Interconnects Standard CMOS Integrated Circuit fabrication process as for

memory chips (Moore’s Law)

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Field Programmable Gate Array ‘Simple’ Programmable Logic Blocks Massive Fabric of Programmable Interconnects Standard CMOS Integrated Circuit fabrication process as for

SRAM memory chips (Moore’s Law)

Huge Density of Logic Block ‘Islands’

1,000 … 100,000’s

in a ‘Sea’ of Interconnects

FPGA Architecture

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Logic Blocks

Logic Functions implemented in Look Up Table LUTs. Flip-Flops. Registers. Clocked Storage elements. Multiplexers (select 1 of N inputs)

16-bit SR

flip-flop

clock

muxy

qe

abcd

16x1 RAM

4-inputLUT

clock enable

set/reset

FPGA Fabric Logic Block

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Look Up Tables LUTs

LUT contains Memory Cells to implement small logic functions Each cell holds ‘0’ or ‘1’ . Programmed with outputs of Truth Table Inputs select content of one of the cells as output

16-bit SR

flip-flop

clock

muxy

qe

abcd

16x1 RAM

4-inputLUT

clock enable

set/reset

3 Inputs LUT -> 8 Memory Cells

SRAM

Static Random Access MemorySRAM cells

SRAM

3 – 6 Inputs

Multiplexer MUX

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Look Up Tables LUTs LUT contains Memory Cells to implement small logic functions Each cell holds ‘0’ or ‘1’ . Programmed with outputs of Truth Table Inputs select content of one of the cells as output Configured by re-programmable SRAM memory cells

16-bit SR

flip-flop

clock

muxy

qe

abcd

16x1 RAM

4-inputLUT

clock enable

set/reset

3 Inputs LUT -> 8 Memory Cells

SRAM

Static Random Access MemorySRAM cells

SRAM

3 – 6 Inputs

Multiplexer MUX

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Logic Blocks

Larger Logic Functions built up by connecting many Logic Blocks together

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Logic Blocks

Larger Logic Functions built up by connecting many Logic Blocks together

Determined by SRAM cells

SRAM SRAM cells

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Clocked Logic

Registers on outputs. CLOCKED storage elements. Synchronous FPGA Logic Design, Pipelined Logic. FPGA Fabric Pulse from Global Clock (e.g. LHC BX frequency)

16-bit SR

flip-flop

clock

muxy

qe

abcd

16x1 RAM

4-inputLUT

clock enable

set/reset

FPGA Fabric

Clock from Outside world (eg LHC bunch frequency)

Special Routing for Clocks

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Input Output I/O Getting data in and out

01

54

6

7

3

2

General-purpose I/Obanks 0 through 7Up to > 1,000 I/O “pins” (several 100 MHz)

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Input Output I/O Getting data in and out

01

54

6

7

3

2

General-purpose I/Obanks 0 through 7

FPGA

Differential pairs

Transceiver block

Up to > 1,000 I/O “pins” (several 100 MHz)

Special I/O SERIALISERS~ 10 Gbps transfer rates

Optical TRx

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Designing Logic with FPGAs

Design Capture. High level Description of Logic Design.

Graphical descriptions Hardware Description Language (Textual)

Graphical State Diagram

Graphical Flowchart

When clock rises If (s == 0) then y = (a & b) | c; else y = c & !(d ^ e);

Textual HDL

Top-levelblock-levelschematic

Block-level schematic

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Hardware Description Languages

Language describing hardware (Engineers call it FIRMWARE) Doesn’t behave like “normal” programming language ‘C/C++’ Describe Logic as collection of Processes operating in

Parallel Language Constructs for Synchronous Logic

Compiler (Synthesis) Tools recognise certain code constructs and generates appropriate logic

Not all constructs can be implemented in FPGA!

2 Popular languages are VHDL , VERILOG Easy to start learning… Hard to master!

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VHDLENTITY Declaration Input Output to Module (STD LOGIC)

SIGNALS Declaration WIRES

CONCURRENT ASSIGNMENTS

CONDITIONAL ASSIGNMENTS => MULTIPLEXERS

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VHDL

COMPONENT Declaration

PROCESS Declaration. CONCURRENT functions. Synchronous Logic.

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Designing Logic with FPGAs High level Description of Logic Design

Hardware Description Language (Textual)

Compile (Synthesis) into NETLIST. Boolean Logic Gates.

Target FPGA Device Mapping Routing

Bit File for FPGA

Commercial CAE Tools(Complex & Expensive)

Logic Simulation

Gate-levelnetlist

BEGIN CIRCUIT=TEST INPUT SET_A, SET-B, DATA, CLOCK, CLEAR_A, CLEAR_B; OUTPUT Q, N_Q; WIRE SET, N_DATA, CLEAR;

GATE G1=NAND (IN1=SET_A, IN2=SET_B, OUT1=SET); GATE G2=NOT (IN1=DATA, OUT1=N_DATA); GATE G3=OR (IN1=CLEAR_A, IN2=CLEAR_B, OUT1=CLEAR); GATE G4=DFF (IN1=SET, IN2=N_DATA, IN3=CLOCK, IN4=CLEAR, OUT1=Q, OUT2=N_Q);

END CIRCUIT=TEST;

Fully-routed physical(CLB-level) netlist

Schematiccapture

Mapping

Packing

Place-and-Route Timing analysis

and timing report

Gate-level netlistfor simulation

SDF (timing info)for simulation

Design Flow

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Bit File for FPGA


Logic Simulation

Gate-levelnetlist



END CIRCUIT=TEST;


Schematiccapture

Mapping

Packing


and timing report



Design Flow

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Bit File for FPGA


Logic Simulation

Gate-levelnetlist



END CIRCUIT=TEST;


Schematiccapture

Mapping

Packing


and timing report



Design Flow

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Configuring an FPGA Millions of SRAM cells holding LUTs and Interconnect Routing Volatile Memory. Lose configuration when board power is

turned off. Keep Bit Pattern describing the SRAM cells in non-Volatile

Memory e.g. PROM or Digital Camera card Configuration takes ~ secs

Configuration data in

Configuration data out

= I/O pin/pad

= SRAM cell

SRAM

JTAG Port

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Configuring an FPGA Millions of SRAM cells holding LUTs and Interconnect Routing Volatile Memory. Lose configuration when board power is

turned off. Keep Bit Pattern describing the SRAM cells in non-Volatile

Memory e.g. PROM or Digital Camera card Configuration takes ~ secs

Configuration data in

Configuration data out

= I/O pin/pad

= SRAM cell

SRAM

JTAG Testing

JTAG Port

ProgrammingBit File

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Large Complex Functions Re-Programmability, Flexibility.

Massively Parallel Architecture Processing many channels simultaneously cf MicroProcessor

Fast Turnaround Designs Standard IC Manufacturing Processes. Moore’s Law Mass produced. Inexpensive. Many variants. Sizes. Features.

PP Not Radiation Hard Power Hungry No Analogue

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FPGA Trends

State of Art is 40nm on 300 mm wafers Top of range >500,000 Logic Blocks >1,000 pins (Fine Pitched BGA)

Logic Block cost ~ 1$ in 1990 Today < 0.1 cent

Problems Power. Leakage currents. Design Gap

CAE Tools 0.0001

0.001

0.01

0.1

1

1990 1995 2000 2005 2010 2015$

/ L

C

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

1985 1990 1995 2000 2005 2010 2015 2020 2025

Year

Nu

mb

er

of

LC

s

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Summary

Programmable Logic Devices Basics Evolution

FPGA Field Programmable Gate Arrays Architecture

Design Flow Hardware Description Languages Design Tools

Importance for Particle Physics Experiments

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References

The Design Warrior’s Guide to FPGAs Clive Maxfield, Newnes Elsevier

VHDL for Logic Synthesis Andrew Rushden, Wiley

FPGA manufacturer web sites www.xilinx.com www.altera.com

FPGA Online www.pldesignline.com www.fpgajournal.com www.doulos.com

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Spare Slides

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System on a Chip

Add Embedded Micro-Processor Cores in Fabric e.g. RISC PowerPC Ethernet Interface

Run Operating System e.g. Linux

Combine Micro-Processor

& Massively Parallel Logic

Dual Design Flows Firmware HDL Software C

uP

(a) One embedded core (b) Four embedded cores

uP uP

uP uP

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Time line of Programmable devices

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FPGAs

ASICs

CPLDs

SPLDs

Microprocessors

SRAMs & DRAMs

ICs (General)

Transistors

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Application Specific Integrated Circuits ASICs

PLDs ASICs

Standard Cell

Full Custom

Gate Arrays

Structured ASICs*

SPLDs

CPLDs

*Not available circa early 1980s

TheGAP

Large Complex Functions . Millions of GatesCustomised for Extremes of Speed, Low Power, Radiation Hardness

(Very) Expensive to Design (in small quantities) > $1 Million mask set(Very) Hard to Design.Long Design cycles.NOT Reprogrammable. FROZEN in Silicon. High Risk

Limited ComplexityThousands of Gates

CheapEasy to DesignReprogrammable.

Custom FabricatedDesign from Scratch

PrefabricatedProgrammed

Documents

Introduction to Programmable Logic Devices