1. Digital Engineering Laboratory Course Introduction & FPGA Concepts and Design
ECE 554
Department of Electrical and Computer Engineering
University of Wisconsin - Madison
4/22/2017

2. Instructors and Course Website
Nam Sung Kim,
Office: 4615 Engineering Hall
Office hours: Tue,Wed,Thur - 2:00 to 3:00 PM
Additional hours by appointment
Chunhua Yao,
Teaching Assistant for Labs
Office hours are assigned lab hours – 3:30 to 6:30 Tuesday and Thursday
The course website and wiki are at:
2017/4/22

3. Course Objectives
Deal with problems and solutions associated with many aspects of a large digital design project
Work effectively as a member of a moderate-sized team
Use contemporary commercial design tools
Use programmable user-defined devices (FPGAs) for rapid prototyping
Learn to live on Pizza and get by on very little sleep  at least during the last part of the course.
4/22/2017

4. Prerequisites and Location
ECE 351 – Digital Logic Laboratory
ECE/CS 552 – Introduction to Computer Architecture
ECE Digital System Design and Synthesis (strongly recommended)
Laboratory: 3628 Engineering Hall
Lecture: 3444 EH
Lectures and Reviews during Lab Hours: 3444 EH
4/22/2017

5. Access to the lab Laboratory: 3628 Engineering Hall
The lab access is password protected and you will have access to the lab 24/7
Password
4/22/2017

6. Course Overview Grading
15% Miniproject – due 2/5
Design a Special Purpose Asynchronous Receiver/Transmitter (team of 2)
20% Bench Exam – on 2/26
Designed to test your understanding of Design Specifications, Verilog, Debugging, Lab Environment, etc. (individual)
65% Project – demos 5/5, report 5/14
Design, implement, test, and program a general or special purpose digital computer that emphasizes some particular features (team of 4 to 6)
2017/4/22

7. Miniproject For the miniproject, you will
Design a Special Purpose Asynchronous Receiver/Transmitter (SPART) and its testbench in Verilog/VHDL and use EDK toolset
Simulate the design to ensure correct performance
Download the design and associated files and demonstrate correct functionality
Preparing a report on your design
4/22/2017

8. Midterm Bench Exam
You will be given a set of specifications for a small system along with Verilog code for some pre-designed modules for the system.
You will be expected to:
Understand the specifications
Understand the Verilog code provided
Write one or more Verilog modules
Debug one or more Verilog modules
Simulate one or more modules and the entire system
Synthesize and implement the design
Download, test, and demonstrate the design on the FPGA board
4/22/2017

9. Project
Design, simulate, synthesize, test, download and demonstrate a non-trivial computer with an original instruction set architecture (ISA)
Four key requirements
It must be an original ISA (somewhat negotiable)
It must be non-trivial
It must be tractable - everything takes at least twice as long as you expect
It must interface through the serial port with the terminal emulator on the lab workstations (negotiable)
Often has significant software component and utilizes FPGA board interfaces
4/22/2017

10. Project Milestone Several major milestones For details see:
Project team selection – each team of 5 or 6 (2/3)
Project proposal presentation (2/12)
Architecture review presentation (2/19)
ISA report due (2/24)
Microarchitecture review presentation (3/24)
Testing and demo review presentation (4/7)
Several progress reviews (see syllabus)
Project demonstrations (5/5)
Project report due (5/14)
For details see:
2017/4/22

11. Major Lab Enhancement
We have done a major enhancement to the ECE554 lab recently, bear with us for version updates
All new computers and monitors
All new FPGA boards and updated digital design software
Overall objectives of the lab will stay the same
Some additional changes may happen this semester
We will try to make the transition as smooth as possible – thanks to Mitch
Go over the syllabus
4/22/2017

12. FPGA Concepts and Design
CMOS IC design alternatives
RAM cell-based FPGA uses
The Xilinx Virtex Series FPGA technology
The Xilinx Integrated Software Environment (ISE) design process
4/22/2017

13. CMOS IC Design Alternatives
STANDARD IC
ASIC
FULL
CUSTOM
SEMI-
CUSTOM
FIELD
PROGRAM-
MABLE
STANDARD
CELL
GATE ARRAY,
SEA OF GATES
FPGA
CPLD
Field Programmable Gate Array (FPGA) – a hardware device with programmable logic, routing, memory, and I/O
4/22/2017

14. RAM Cell-Based FPGA Uses
Prototyping gate array, standard cell, or full custom integrated circuits (ICs)
Prototyping complete systems
Implementing “hardware simulation”
Replacing ICs
Providing multifunction reconfigurable system ICs
Hardware accelerators
4/22/2017

15. Xilinx Virtex FPGA Architecture
Primary Reference:
On-Line Xilinx Data Sheet DS003 (v.2.5, April 2, 2001) -
Figure 1: Virtex Architecture Overview
IOBs - Input/Output Blocks
CLBs - Configurable Logic Blocks
Function generators, Flip-Flops, Combinational Logic, and Fast Carry Logic
GRM - General Routing Matrix
BRAMs - Block SelectRAM (configurable memory)
DLLs - Delay-Locked Loops for clock control
VersaRing - I/O interface routing resources
4/22/2017

16. Figure 1- Virtex Architecture Overview
4/22/2017

17. RAM-based FPGA
Xilinx XC4000ex
4/22/2017

18. Virtex FPGA Architecture
Logic configured by values stored in SRAM cells
CLBs implement logic in SRAM-stored truth tables
CLBs also use SRAM-controlled multiplexers
Routing uses “pass” transistors for making/breaking connections between wire segments
Block RAMs allow programmable memories with configurable widths (1, 2, 4, 8, or 16 bits)
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19. Look-up Table Based Logic Cell
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20. Programmable Routing
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21. Table 1 – Virtex FPGA Family Members
We use the XCV800 device
0.22 micron, five-layer metal process
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22. IOB - Input/Output Block
See Figure 2: Virtex Input/Output Block
Separate signals for input (I), output (O), and output enable (T)
Three storage elements function as D flip-flops or latches with clock enable (CE) and set/reset (SR)
I/O pins can connect directly to internal logic or through the storage element
Programmable input delay
3-state output buffer
I/O pad can use pull-up, pull-down, or weak keeper
Supports a wide range of voltages
4/22/2017

23. Figure 2: Virtex Input/Output Block
4/22/2017

24. CLB - Configurable Logic Block
See Figure 4: 2-Slice Virtex CLB
Each slice contains two logic cells (LCs) and consists of
2 4-input look-up tables (LUTs)
2 D flip-flops/latches
Fast carry and control logic
Three-state drivers
SRAM control logic
4/22/2017

25. Figure 4: 2-Slice Virtex CLB
4/22/2017

26. CLB - Configurable Logic Block
See Figure 5: Detailed View of Virtex Slice
Logic Function Implementation
2 Function Generators - Each a 4-input LUT - implements any 4-input function
F5 multiplexer - combines two LUTs with select input - implements any 5-input function, 4-to-1 mux, or selected functions of up to 9 inputs.
F6 multiplexer - combines outputs of two F5 multiplexer - implements any 6-input function, 8-to-1 mux, or selected functions of up to 19 inputs.
Four direct feedthrough paths - useful to facilitate routing by use of through-the-cell paths
4/22/2017

27. Figure 5: Detailed View of Virtex Slice
4/22/2017

28. CLB - Configurable Logic Block
Storage Elements
2 D flip-flops/latches
Optionally included in cell output paths
Shared clock enable
Shared synchronous/asynchronous Set/Reset signals
SR - forces storage element into initialization state specified (0 or 1)
BY - forces storage element into opposite state
4/22/2017

29. CLB - Configurable Logic Block
Fast Carry Logic (See Figures 4 and 5)
Two chains of two bits per CLB
AND gate (for mult), 0/1 Mux, CY Mux, EXOR
3-state Drivers (BUFT) - on-chip drivers with independent control and input pins
Distributed LUT SelectRAMs – one per logic cell, 2 LUTs can be reconfigured as one of:
Two 16 x 1-bit synchronous RAM
16 x 2-bit synchronous RAM
32 x 1-bit synchronous RAM
16 x 1-bit dual-port synchronous RAM
Two 16-bit shift registers
4/22/2017

30. Block SelectRAM Fully synchronous dual-ported 4096-bit RAM
Stores address, data and write-control signal on inputs at clock edge
Cannot change address, even for read, without using clock
Independent control signals for each port
Organized in vertical columns of blocks on left and right of CLB array
Block height is 4 CLBs => Number of block RAMs per column is (height of CLB of array)/4
See Tables 3 & 4 and Figure 6.
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31. Tables 3 & 4 and Figure 6
4/22/2017

32. Programmable Routing Matrix
Local Routing
See Figure 7: Virtex Local Routing
Interconnections among LUTs, flip-flops, and General Routing Matrix (GRM)
Internal CLB feedback paths that can chain LUTs together
Direct paths between horizontally-adjacent CLBs
Short connections with few “pass” transistors => low delay => high-speed connections
Combination of hardware and software is used to try to minimize routing delay
4/22/2017

33. Figure 7: Virtex Local Routing
4/22/2017

34. Programmable Routing Matrix
General Purpose Routing
Majority of interconnect resources
In horizontal and vertical routing channels associated with rows and columns of CLBs
GRM - Switch matrix through which horizontal and vertical routing resources connect and means by which CLBs access general purpose routing
24 single-length lines between adjacent GRMs in 4 directions
12 buffered hex lines route GRM signals to other GRMs 6 blocks away in 4 directions (can be accessed 3 or 6 blocks away)
12 longlines are buffered bidirectional wires that distribute signals across the device
Vertical - span full device height
Horizontal - span full device width
4/22/2017

35. Programmable Routing Matrix
I/O Routing
VersaRing
Supports pin-swapping and pin-locking
Facilitates pin-out flexibility
Dedicated Routing (not programmable)
Four partitionable bus lines per CLB row driven by BUFTs (See Figure 8: BUFT Connections)
Two dedicated nets per CLB for vertical carry signals to adjacent cells
4/22/2017

36. Figure 8: BUFT Connections
4/22/2017

37. Programmable Routing Matrix
Global Routing
Distribute clocks and other signals with high fanout
Primary Global Routing
Four dedicated global nets with dedicated input pins for clocks
Driven by global buffers
Can drive all CLB, IOB, and BRAM clock pins
Secondary Global Routing
24 backbone lines, 12 across top of chip and 12 across bottom of chip
From these, can distribute 12 unique signals/column via 12 longlines in column
Not restricted to routing only to clock pins
4/22/2017

38. Clock Distribution Via primary global routing resources
See Figure 9: Global Clock Distribution Network
Four global buffers
Two at top center
Two at bottom center
Four dedicated clock input pads
Input to global buffers from pads or from general purpose routing
4/22/2017

39. Figure 9: Global Clock Distribution Network
4/22/2017

40. Delay-Locked Loops (DLLs)
One associated with each clock buffer
Eliminate skew between clock input pad and internal clock-input pins within the device
Each can drive two global clock networks
Clock edges reach internal flip-flops 1 to 4 clock periods after they arrive at the input.
Provides control of multiple clock domains
Has minimum clock frequency restrictions!
4/22/2017

41. Table 1 and Figures 4 & 7
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42. Boundary Scan IEEE(ANSI) Standard 1149.1
Provides Ability to Observe and Control I/O pins
Accessed Through a Standard Test Access Port (TAP)
Additional Logic Includes Test Instruction Register, ID Register, two User Registers and a One Bit Bypass Register.
Uses:
Test Interconnects between ICs on Boards
Perform Tests on Internal Logic
Initialize Built-In Self-Test (BIST) Logic
Perform Sampling During Normal Operation
4/22/2017

43. Configuration How is the FPGA configured? Implemented by
Clearing configuration memory
Loading configuration data into 2-D configuration SRAM
Activating logic via a startup process
Configuration Modes
Slave-Serial – FPGA receives bit-serial data (e.g., from PROM) synchronized by an external clock
Master-Serial - FPGA receives bit-serial data (e.g., from PROM) synchronized by FPGA clock
SelectMAP - Byte-wide data is written into the FPGA with a BUSY flag from FPGA controlling the flow of data
Boundary-scan – Configuration is done through the Test Access Port
The XCV800 device requires 4,715,616 configuration bits
4/22/2017

44. XCV800 Characteristics Maximum Gate Count 888,439 CLB Matrix 56 x 84
Logic Cells 21,168
Maximum IOBs 512
Flip-Flop Count 43,872
Block RAM Bits ,688
Horizontal TBUF Long Lines 224
TBUFs per Long Line 168
Program Data (bits) 4,715,616
4/22/2017

45. THE ECE 554 XILINX DESIGN PROCESS
Design process overview
Design reference
Design tutorial
What’s next
4/22/2017

46. Design Process Steps Definition of system requirements.
Example: ISA (instruction set architecture) for CPU.
Includes software and hardware interfaces with timing.
May also include cost, speed, power, reliability and maintainability specifications.
Definition of system architecture.
Example: high-level HDL (hardware description language) representation - this is optional in ECE 554, but is done in the real world).
Useful for system validation and verification and as a basis for lower level design execution and validation or verification.
4/22/2017

47. Design Process Steps(continued)
Refinement of system architecture
In manual design, descent in hierarchy, designing increasingly lower-level components
In synthesized design, transformation of high-level HDL to “synthesizable” register transfer level (RTL) HDL
Logic design or synthesis
In manual or synthesized design, development of logic design in terms of library components
Result is logic level schematic or netlist representation or combinations of both.
Both manual design and synthesis typically involve optimization of cost, area, or delay.
4/22/2017

48. Design Process Steps (Continued)
Implementation
Conversion of the logic design to physical implementation
Involves the processes of:
Mapping of logic to physical elements,
Placing of resulting physical elements,
And routing of interconnections between the elements.
In case of SRAM-based FPGAs, represented by the programming bitstream which generates the physical implementation in the form of CLBs, IOBs, BRAMs, and the interconnections between them
4/22/2017

49. Design Process Steps (continued)
Validation – test and debug (used at several steps in the process)
At architecture level - functional simulation of HDL
At RTL level - functional simulation of RTL HDL
At logic design or synthesis - functional simulation of gate-level circuit - not usually done, but recommended in ECE 554
At implementation - timing simulation of schematic, netlist or HDL with implemention based timing information (functional simulation can also be useful here)
At programmed FPGA level - in-circuit test of function and timing
4/22/2017

50. Xilinx HDL/Core Design Flow
DESIGN ENTRY
RTL HDL EDITING
CORE GENERATION
RTL HDL-CORE
SIMULATION
SYNTHESIS
IMPLEMENTATION
TIMING
SIMULATION
FPGA PROGRAMMING
& IN-CIRCUIT TEST
4/22/2017

51. Xilinx HDL/Core Design Flow - HDL Editing
Accessed within
ISE Foundation
DESIGN WIZARD
LANGUAGE ASSISTANT
HDL Module Frameworks
Language Construct Templates
HDL EDITOR
RTL HDL Files
4/22/2017

52. Xilinx HDL/Core Design Flow - Core Generation
Select core and specify input parameters
CORE GENERATOR
HDL instantiation module for core_name
EDIF netlist for core_name
Other core_name files
4/22/2017

53. Xilinx HDL/core Design Flow - HDL Functional Simulation
HDL instantiation module for core_names
Set Up and Map work Library
RTL HDL Files
EDIF netlists for core_names
Testbench HDL Files
Compile HDL Files
Test Inputs or Force Files
MODELSIM
Functional Simulate
Waveforms or List Files
4/22/2017

54. Xilinx HDL Design Flow - Synthesis
All HDL Files
Edit FPGA Express Synthesis Constraints
EDIF netlists for core_names
Select Top Level
Synthesis/Implement-ation Constraints
Select Target Device
Xilinx ISE
Synthesize
Gate/Primitive Netlist Files (EDIF or XNF)
Synthesis Report Files
4/22/2017

55. Xilinx HDL/core Design Flow - Implementation
Gate/Primitive Netlist Files (XNF or EDN)
Netlist Translation
XILINX ISE
Map
Place & Route
Model Extraction
Timing Model Gen
HDL or EDIF for Implemented Design
Create Bitstream
Standard Delay Format File
BIT File
4/22/2017

56. Xilinx HDL/core Design Flow - Timing Simulation
HDL or EDIF for Implemented Design
Standard Delay Format File
Set Up and Map work Directory
Testbench HDL Files
Compile HDL Files
MODELSIM
Test Inputs, Force Files
Compiled HDL
HDL Simulate
Waveforms or List Files
4/22/2017

57. Xilinx HDL Design Flow - Programming and In-circuit Verification
Bit File
Input Byte
GXSLOAD
GXSPORT
ECE 554 FPGA Board
Other Inputs
Outputs
4/22/2017

58. Design Practices Use synchronous design.
CLBs are actually reading functions from SRAM
Avoid clock gating.
Avoid ripple counters.
Avoid use of direct sets and resets except for initialization.
Synchronize asynchronous signals as needed.
Test and debug each component design
Rule of 10: it requires ten times more effort to debug a design that has untested components in it.
4/22/2017

59. What’s Next
HDL/core design flow – design tutorial will employ the flow described for a Verilog HDL/core example
During lab time on Tuesday
Read over the tutorial before coming to lab
Find a partner for the miniproject by next Tuesday
Start looking over the course website
If you feel rusty with Verilog, take a look at lecture 2
4/22/2017

60. Tutorial Overview
Use the tools in the lab to design, simulate, and implement a simple design
Use of embedded tool kit to help implement the miniproject
Multiply-accumulate unit
Main steps include
Performing HDL coding for synthesis (Xilinx ISE)
Using cores (Xilinx Core Generator)
Behavioral simulation of synthesizable HDL code (ModelSim)
Design synthesis (translation) (Xilinx ISE)
Design implementation (map, place & route) (Xilinx ISE)
Timing (post-Implementation) simulation (ModelSim)
Generating the FPGA programming file (Xilinx ISE)
4/22/2017