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

Instructors and Course Website Nam Sung Kim, nskim3@wisc.edu Office: 4615 Engineering Hall Office hours: Tue,Wed,Thur - 2:00 to 3:00 PM Additional hours by appointment Chunhua Yao, yao1@wisc.edu 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: http://homepages.cae.wisc.edu/~ece554/new_website/ https://cgi.cae.wisc.edu/~ece554/pmwiki/pmwiki.php 2017/4/22

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

Prerequisites and Location ECE 351 – Digital Logic Laboratory ECE/CS 552 – Introduction to Computer Architecture ECE 551 - 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

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

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

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 https://cgi.cae.wisc.edu/~ece554/pmwiki/pmwiki.php?n=Main.MiniProject 4/22/2017

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

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

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: https://cgi.cae.wisc.edu/~ece554/pmwiki/pmwiki.php?n=Main.Milestones 2017/4/22

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

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

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

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

Xilinx Virtex FPGA Architecture Primary Reference: On-Line Xilinx Data Sheet DS003 (v.2.5, April 2, 2001) - http://www.xilinx.com/partinfo/ds003.pdf 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

Figure 1- Virtex Architecture Overview 4/22/2017

RAM-based FPGA Xilinx XC4000ex 4/22/2017

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) 4/22/2017

Look-up Table Based Logic Cell 4/22/2017

Programmable Routing 4/22/2017

Table 1 – Virtex FPGA Family Members We use the XCV800 device 0.22 micron, five-layer metal process 4/22/2017

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

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

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

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

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

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

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

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

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. 4/22/2017

Tables 3 & 4 and Figure 6 4/22/2017

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

Figure 7: Virtex Local Routing 4/22/2017

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

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

Figure 8: BUFT Connections 4/22/2017

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

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

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

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

Table 1 and Figures 4 & 7 4/22/2017

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

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

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 114,688 Horizontal TBUF Long Lines 224 TBUFs per Long Line 168 Program Data (bits) 4,715,616 4/22/2017

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 https://cgi.cae.wisc.edu/~ece554/pmwiki/pmwiki.php?n=Documentation.Tutorial 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

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