FPGA NightClass #1Unallocated Space, Severn MDfpga@unallocatedspace.orgPresenter: David Protzman

Agenda Instructor Intro Class History Things That Will Be Covered

Instructor IntroName: Dave / ProtoJob: Cloud Software DeveloperElectronics Background:

ArduinoPICVHDLXilinx

Class History Started May 7th, 2013 Ended March X, 2014 Covered:

7 Segments LCD 16x2 Displays Computer Monitor Displays Custom 8-bit CPU SRAM Interface With SPI

Why Restart? Too in depth, too quickly Became very focused

What to Expect Basics of FPGA fabric Using Xilinx ISE Introduction to VHDL Simple IO (buttons, leds, etc) Clocking Combinatorial and sequential logic State machines Interface with SRAM and 16x2 LCD screens VGA interface (easier than you might think!) Requests!

Tonights Plan What is an FPGA? A word about CPLDs How does it compare to microcontrollers/CPUs? Why use an FPGA? How are FPGAs programmed? What is an FPGA made of? What are the different Xilinx FPGAs? Why not Xilinx and Altera mix? What do I need to start programming? Live demo of ISE Upload Hello World blinky light example bit file

What is an FPGA? FPGA: A field-programmable gate array (FPGA) is an integrated circuit

designed to be configured by a customer or a designer after manufacturinghence "field-programmable" (Wikipedia)

Almost any digital circuit Made of LOTS of gates Screwed up? No worries, just reprogram it!

A Word About CPLDs Complex Programmable Logic Devices

Sort of baby FPGAs Consist of macro cells Nowhere near as many gates as an FPGA Much cheaper Still programmable like an FPGA Can also replicate digital circuits Can be used for smaller, simpler designs

Ethernet Just need lots of IO, but not a lot of speed Level shifter PWM driver

We will not be covering anything else about CPLDs

FPGAs and Microcontrollers Microcontrollers:

Good for quick turnaround development Lots of already baked in functionality (serial, I2C, SPI, etc) Cheap Breadboardable (sometimes) Moderately fast Programmed in C/C++/assembly Generally low pin count Mostly single threaded

FPGAs and Microcontrollers FPGAs:

Can be anything you want Programmed with VHDL/Verilog Need to develop your own peripherals Parallel by default Not breadboardable Expensive compared to microcontrollers Takes a while to program Completely different way of thinking about a problem Need a 200 MHz sine generator and 2 FFT modules? No Problem!

FPGAs and Microcontrollers FPGAs seem difficult right? Why use them at all?

Need lots of IO? FPGAs have a high pin count

Real time processing? FPGAs can run over 200MHz in parallel

Lots of things happening at the same time? Everything can happen at once on an FPGA

Want one chip with 64 SPI interfaces? Create as many instances of a module as you want!

FPGA - Programming Our boards use JTAG JTAG:

Joint Test Action Group IEEE 1149.1 Provides debugging, programming, and user access

Most FPGA development boards have onboard USB to JTAG No need for JTAG programmers Even so, most boards expose the JTAG header anyway Activity: Find the JTAG header on your board

FPGA - Programming An FPGAs program is volatile

Once the power goes off, the program is lost EEPROMs to the rescue!

Most FPGA boards will have some kind of EEPROM to store the program

These EEPROMs are also sometimes JTAG devices In this case, they will either be daisy chained, or have a separate

JTAG header

FPGA - What is Inside? This varies chip to chip Here are some of the things we should all have

Flip-Flops Slices CLBs (Configurable Logic Blocks) RAM (Random Access Memory) DSPs (Digital Signal Processors) DCMs (Digital Clock Managers) IO Buffers

FPGA Parts - Flip-Flop Flip-flop: A 1 bit circuit that has two stable states and can be used to store

state information (Wikipedia) An FPGA can be thought of as a massive array of flip-flops. Flip-flops can be connected together to store larger amounts of

information.

FPGA Parts - Flip-Flop We are interested in the D Flip-Flop

Clocked on the rising edge (there are no falling edge flip-flops in an FPGA)

Has a reset pin that clears sets Q to zero Has a set pin that will set Q to one

Cannot use set and reset together!!! Forms the basis for the shift register

FPGA Parts - Lookup Table Lookup Table: Basically a small RAM block that can be used to implement

logic functions Example: You want to make sure that when inputs A and B are

pressed that C goes high.

A B C

0 0 0

0 1 0

1 0 0

1 1 1

FPGA Parts - Slices Slices: Xilinx term for groupings of logic in the FPGA Spartan 6 slice types (http://www.xilinx.

com/support/documentation/user_guides/ug384.pdf page 7) SLICEX: 6-input LUT, 8 Flip-flops SLICEL: 6-input LUT, 8 Flip-flops, wide muxes, carry logic SLICEM: 6-input LUT, 8 Flip-flops, wide muxes, carry logic, distributed

RAM, shift registers Spartan 6

2 Slices = 8 lookup tables + 16 Flip Flops Spartan 3

4 Slices = 4 lookup tables + ? Flip Flops

FPGA Parts - CLB CLB: Configurable Logic Block These are the main logic resources Spartan 6

1 CLB = 2 Slices Spartan 3

1 CLB = 4 Slices Arranged in a grid on the physical FPGA chip

FPGA - RAM 2 types of RAM

Distributed Uses FPGA fabric Takes up logic resources

Distributed RAM is made of LUTs

Block Dedicated blocks of memory on

the die Does not take up logic resources

FPGA - DSP DSP: Digital Signal Processing Common DSP functions in FPGAs

Digital signal filters (FIR, CIC, DDC) Complex numbers CORDIC (sine, cos, tan, etc) DFT, FFT DDS Multiply accumulate Floating point

Dedicated space on the die

FPGA - DCM DCM: Digital Clock Manager Used to create various clock rates and phases

Ex: You have a base clock of 100 MHz, but need 150 MHz DCM with a multiply of 3 and divide of 2

100 MHz * 3 = 300 MHz 300 MHz / 2 = 150 MHz

Not able to synthesize all frequencies Limited number available Dedicated space on the die Generally able to multiply and divide by up to 32

We will be using these a lot! Note: Not able to go very low in frequency!!!

FPGA Parts - IO Connect to the physical pins on the FPGA Several Types:

Clocks JTAG Differential Tri-State Wake Init Others

FPGA Parts - IO Cont. Class activity:

Spartan 6 (Mojo and Nexys3) http://www.xilinx.com/support/documentation/user_guides/ug385.

pdf Find your chip

Mojo - TQG144 Package--LX4 and LX9 page 272 Nexys 3 - CSG324 Package--LX16 page 279

Spartan 3 (Basys2) http://www.xilinx.com/support/documentation/data_sheets/ds099.

pdf Find your chip

Basys2 - CP132 Footprint page 140

FPGA Parts - IO Cont. Locate the following:

User IO CCLK VREF GCLK A## TCK, TDI, TDO, TMS VCCINT, VCCAUX, VCCO, GND

FPGA Parts - IO Cont. IO is divided into Banks Locate Bank 1 Each bank has one or more VCCO inputs

VCCO determines the input and output voltage of the bank Allows each bank to have different voltage input and output

Most boards have all banks tied together, or have jumpers to select voltage for certain banks

Xilinx We use Xilinx FPGAs for this class There are two main FPGA vendors

Xilinx Have the majority share, and are more expensive

Altera Not as much of the market, but cheap and effective

There is a third, not so well known vendor Lattice Semiconductor

Small, low power FPGAs

Xilinx - Types of FPGAs Two main series of FPGAs from Xilinx (6 series only)

Spartan Aimed at educational institutions Not as full featured as Virtex and a little slower MUCH cheaper - Most expensive on Digikey: $317.50 Not as many pins (Largest is 900 pins)

Virtex About 1.5x faster More logic elements available More resources VERY expensive - Most expensive on Digikey: $39,452.40 Lots and lots of pins (Largest is 1925 pins) Some have embedded PowerPC processors

Xilinx - Series Numbers Spartan:

1-6 Virtex:

1-7 Artix

7 Kintex

7 Easy Path

6

Mixing FPGA Brands This class only focuses on Xilinx Xilinx and Altera both have IDEs (Integrated Development Environments)

These are not the same! They are not compatible

Different IP Cores IP Cores are Xilinxs name for pre-built modules

DDR interface Ethernet MII interface Various math modules

Not sure what Altera calls them Teaching both would be difficult Mainly: Your instructor only knows Xilinx!!

FPGA - Writing Programs Most important thing:

You do NOT program an FPGA!!! You describe a digital circuit for an FPGA

Pick an HDL (Hardware Description Language) Verilog

Popular in USA, Asia, India, and South America Very C-like

VHDL (VHSIC Hardware Description Language) Developed by the US govt Based on Ada and Pascal Very verbose and strict Popular in Europe

VHDL - Why? Why are we using VHDL?

Short answer: Its all I know Other answers:

VHDL is more strict than Verilog Builds character!

VHDL is more verbose Leads to a better understanding

You can still use Verilog code Xilinx tools convert for you!

Xilinx - Getting started ISE

Stands for Integrated Software Environment Requires a license (free for us!)

We will be using the Web Pack Only supports the lower end FPGAs Does not have all the bells and whistles

You can get a 30 day license for the Design Suite Has all the cool stuff!

Consists of many different programs Project Navigator Simulator Floor Planner Others

ISE Project Navigator Youll spend most of your time here Some of the things to do:

Create new VHDL files Add Xilinx IP Cores Create test benches Build your bitstream

1. Synthesize 2. Translate 3. Map 4. Place and route 5. Generate bitstream

Xilinx - ISE

Project Navigator - DesignCurrent project

FPGA chip package

VHDL file called class_cpu.vhd

Xilinx IP Core cpu_divider * Xilinx IP Core memory *

ChipScope instance **

Means this is the main VHDL file

VHDL file called cpu_instructor_copy.vhd

Constraints file

* : This is not the name of the IP Core, just the instance of this IP Core

** : We will not cover this for a while

Xilinx - ISE

Project Navigator - ProcessesDisplay reports about FPGA utilization, timing, etcMake a symbol for the

schematic editorShow VHDL code for creating an instance of this designAdd timing requirements

GUI for defining what pins connect to what in your designView/Edit the actual layout

of FPGA resourcesEnsure design can be run in FPGARuns Translate, Map, and

Place & Route Prepares netlist and constraints for Map processConverts netlist and constraints

to FPGA resources Places FPGA resources and routes connections

Generates bit file for programming the FPGA

Project Navigator - Console

Shows all output (includes errors and warnings too)

Shows just errors

Shows just warnings

Project Navigator - Summary

This page will show information about how your design fits on the FPGA and what resources were used to fit your design to the FPGA.We will go more in depth later on!