Xilinx System Generator User Guide

System
Generator for
DSP
User Guide
Release 10.1.1
April, 2008
R
R
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System Generator for DSP
www.xilinx.com
Release 10.1.1
April, 2008
Table of Contents
Preface: About This Guide
Guide Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System Generator PDF Doc Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Typographical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Online Document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Chapter 1: Hardware Design Using System Generator
A Brief Introduction to FPGAs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Note to the DSP Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Note to the Hardware Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Design Flows using System Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Algorithm Exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Implementing Part of a Larger Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Implementing a Complete Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
System-Level Modeling in System Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
System Generator Blocksets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Signal Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bit-True and Cycle-True Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Timing and Clocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Synchronization Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block Masks and Parameter Passing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Resource Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Automatic Code Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Compiling and Simulating Using the System Generator Block . . . . . . . . . . . . . . . . . . 39
Compilation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
HDL Testbench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Compiling MATLAB into an FPGA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Simple Selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Simple Arithmetic Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Complex Multiplier with Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Shift Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Passing Parameters into the MCode Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Optional Input Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Finite State Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parameterizable Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FIR Example and System Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RPN Calculator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Example of disp Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Importing a System Generator Design into a Bigger System . . . . . . . . . . . . . . . . . . 71
HDL Netlist Compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Integration Design Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
New Integration Flow between System Generator & Project Navigator . . . . . . . . . . .
A Step-by-Step Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Configurable Subsystems and System Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Defining a Configurable Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using a Configurable Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Deleting a Block from a Configurable Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adding a Block to a Configurable Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Generating Hardware from Configurable Subsystems . . . . . . . . . . . . . . . . . . . . . . . . . 85
Notes for Higher Performance FPGA Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Review the Hardware Notes Included in Block Dialog Boxes . . . . . . . . . . . . . . . . . . .
Register the Inputs and Outputs of Your Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Insert Pipeline Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Use Saturation Arithmetic and Rounding Only When Necessary . . . . . . . . . . . . . . . .
Use the System Generator Timing Analysis Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Set the Data Rate Option on All Gateway Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reduce the Clock Enable (CE) Fanout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Processing a System Generator Design with FPGA Physical Design Tools . . . . 88
HDL Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Generating an FPGA Bitstream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Resetting Auto-Generated Clock Enable Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
ce_clr and Rate Changing Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
ce_clr Usage Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Design Styles for the DSP48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
About the DSP48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Designs Using Standard Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Designs Using Synthesizable Mult, Mux and AddSub Blocks . . . . . . . . . . . . . . . . . . . 99
Designs that Use DSP48 and DSP48 Macro Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
DSP48 Design Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Using FDATool in Digital Filter Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Design Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open and Generate the Coefficients for this FIR Filter . . . . . . . . . . . . . . . . . . . . . . . .
Parameterize the MAC-Based FIR Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generate and Assign Coefficients for the FIR Filter . . . . . . . . . . . . . . . . . . . . . . . . . . .
Browse Through and Understand the Xilinx Filter Block . . . . . . . . . . . . . . . . . . . . . .
Run the Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Generating Multiple Cycle-True Islands for Distinct Clocks . . . . . . . . . . . . . . . . 114
Multiple Clock Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Clock Domain Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crossing Clock Domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Netlisting Multiple Clock Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Step-by-Step Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Creating a Top-Level Wrapper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Using ChipScope Pro Analyzer for Real-Time Hardware Debugging . . . . . . . . 126
ChipScope Pro Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ChipScope in System Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Real-Time Debug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Importing Data Into MATLAB Workspace From ChipScope . . . . . . . . . . . . . . . . . . .
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Chapter 2: Hardware/Software Co-Design
Hardware/Software Co-Design in System Generator . . . . . . . . . . . . . . . . . . . . . . . . 138
Black Box Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
PicoBlaze Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
EDK Processor Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Integrating a Processor with Custom Logic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Memory Map Creation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hardware Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generating Software Drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Writing Software for EDK Processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Asynchronous Support for EDK Processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
EDK Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Importing an EDK Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Exposing Processor Ports to System Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Exporting a pcore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Designing with Embedded Processors and Microcontrollers . . . . . . . . . . . . . . . . 148
Designing PicoBlaze Microcontroller Applications . . . . . . . . . . . . . . . . . . . . . . . . . . .
Designing and Exporting MicroBlaze Processor Peripherals . . . . . . . . . . . . . . . . . . .
Tutorial Example - Designing and Simulating MicroBlaze Processor Systems . . . .
Using XPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Chapter 3: Using Hardware Co-Simulation
Installing Your Hardware Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
Ethernet-Based Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
JTAG-Based Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
Third-Party Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
Compiling a Model for Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Choosing a Compilation Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Invoking the Code Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Hardware Co-Simulation Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
Hardware Co-Simulation Clocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Selecting the Target Clock Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
Clocking Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Selecting the Clock Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Board-Specific I/O Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
I/O Ports in Hardware Co-simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Ethernet Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Point-to-Point Ethernet Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
Network-Based Ethernet Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Shared Memory Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
Compiling Shared Memories for Hardware Co-Simulation . . . . . . . . . . . . . . . . . . . .
Co-Simulating Unprotected Shared Memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Co-Simulating Lockable Shared Memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Co-Simulating Shared Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Co-Simulating Shared FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Restrictions on Shared Memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Specifying Xilinx Tool Flow Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Frame-Based Acceleration using Hardware Co-Simulation . . . . . . . . . . . . . . . . . . 201
Shared Memories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adding Buffers to a Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Compiling for Hardware Co-simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using Vector Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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209
Real-Time Signal Processing using Hardware Co-Simulation . . . . . . . . . . . . . . . 214
Applying a 5x5 Filter Kernel Data Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
5x5 Filter Kernel Test Bench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
Reloading the Kernel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
Installing Your Hardware Co-Simulation Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
Installing an ML402 Board for Ethernet Hardware Co-Simulation . . . . . . . . . . . . . . 224
Installing an ML506 Board for Ethernet Hardware Co-Simulation . . . . . . . . . . . . . . 233
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Installing a Spartan-3A DSP 1800A Starter Platform for Ethernet Hardware Co-Simulation242
Installing a Spartan-3A DSP 3400A Development Platform for Ethernet Hardware CoSimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
Installing an ML402 Board for JTAG Hardware Co-Simulation . . . . . . . . . . . . . . . . . 254
Supporting New Platforms through JTAG Hardware Co-Simulation . . . . . . . . 255
Hardware Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
Supporting New Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
Chapter 4: Importing HDL Modules
Black Box HDL Requirements and Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Black Box Configuration Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Black Box Configuration M-Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
HDL Co-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
270
270
272
283
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Configuring the HDL Simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Co-Simulating Multiple Black Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
Black Box Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
Importing a Xilinx Core Generator Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Importing a VHDL Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Importing a Verilog Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dynamic Black Boxes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Simulating Several Black Boxes Simultaneously . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Advanced Black Box Example Using ModelSim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
286
300
307
309
311
313
Chapter 5: System Generator Compilation Types
HDL Netlist Compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
NGC Netlist Compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
Bitstream Compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
XFLOW Option Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
Additional Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
Re-Compiling EDK Processor Block Software Programs in Bitstreams . . . . . . . . . . 324
EDK Export Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Creating a Custom Bus Interface for Pcore Export . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Export as Pcore to EDK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System Generator Ports as Top-Level Ports in EDK . . . . . . . . . . . . . . . . . . . . . . . . . . .
Supported Processors and Current Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
See Also: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
326
327
328
328
328
Hardware Co-Simulation Compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Timing Analysis Compilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Timing Analysis Concepts Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
Timing Analyzer Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
Creating Compilation Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
Defining New Compilation Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Preface
About This Guide
This User Guide provides in-depth discussions on topics that are key to understanding
and using System Generator. In addition, examples and turorials are also provided that
extend beyond the scope of the System Generator Getting Started Guide.
Guide Contents
This User Guide contains information the following topics:
•
Hardware Design using System Generator
•
Hardware Software Co-Design
•
Hardware Co-Simulation
•
Importing HDL Modules
•
System Generator Compilation Types
System Generator PDF Doc Set
This User Guide can be found in the System Generator Help system and is also part of the
System Generator Doc Set that is provided in PDF format. The content of the doc set is as
follows:
•
System Generator for DSP Getting Started Guide
•
System Generator for DSP User Guide
•
System Generator for DSP Reference Guide
Note: Hyperlinks across these PDF documents work only when the PDF files reside in the same
folder. After clicking a Hyperlink in the Adobe Reader, you can return to the previous page by pressing
the Alt key and the left arrow key (←) at the same time.
Additional Resources
To find additional documentation, see the Xilinx website at:
http://www.xilinx.com/literature.
To search the Answer Database of silicon, software, and IP questions and answers, or to
create a technical support WebCase, see the Xilinx website at:
http://www.xilinx.com/support.
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Preface: About This Guide
Conventions
This document uses the following conventions. An example illustrates each convention.
Typographical
The following typographical conventions are used in this document:
Convention
Meaning or Use
Example
Courier font
Messages, prompts, and
program files that the system
displays
Courier bold
Literal commands that you
ngdbuild design_name
enter in a syntactical statement
Helvetica bold
Commands that you select from File →Open
a menu
Keyboard shortcuts
Italic font
{ }
Vertical bar
Ctrl+C
Variables in a syntax statement ngdbuild design_name
for which you must supply
values
Square brackets
Braces
speed grade: - 100
[ ]
References to other manuals
See the Development System
Reference Guide for more
information.
Emphasis in text
If a wire is drawn so that it
overlaps the pin of a symbol,
the two nets are not connected.
An optional entry or parameter. ngdbuild [option_name]
However, in bus specifications, design_name
such as bus[7:0], they are
required.
A list of items from which you lowpwr ={on|off}
must choose one or more
|
Vertical ellipsis
.
.
.
Separates items in a list of
choices
lowpwr ={on|off}
Repetitive material that has
been omitted
IOB #1: Name = QOUT’
IOB #2: Name = CLKIN’
.
.
.
Horizontal ellipsis . . . Repetitive material that has
been omitted
allow block block_name loc1
loc2 ... locn;
Online Document
The following conventions are used in this document:
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Conventions
Convention
Blue text
Meaning or Use
Example
Cross-reference link to a
location in the current
document
See the topic “Additional
Resources” for details.
Red text
Cross-reference link to a
location in another document
See Figure 2-5 in the Virtex-II
Platform FPGA User Guide.
Blue, underlined text
Hyperlink to a website (URL)
Go to http://www.xilinx.com
for the latest speed files.
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Refer to “Title Formats” in
Chapter 1 for details.
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Chapter 1
Hardware Design Using System
Generator
System Generator is a system-level modeling tool that facilitates FPGA hardware design. It
extends Simulink in many ways to provide a modeling environment that is well suited to
hardware design. The tool provides high-level abstractions that are automatically
compiled into an FPGA at the push of a button. The tool also provides access to underlying
FPGA resources through low-level abstractions, allowing the construction of highly
efficient FPGA designs.
A Brief Introduction to FPGAs
Provides background on FPGAs, and discusses
compilation, programming, and architectural
considerations in the context of System Generator.
Design Flows using System
Generator
Describes several settings in which constructing
designs in System Generator is useful.
System-Level Modeling in
System Generator
Discusses System Generator's ability to implement
device-specific hardware designs directly from a
flexible, high-level, system modeling environment.
Automatic Code Generation
Discusses automatic code generation for System
Generator designs.
Compiling MATLAB into an
FPGA
Describes how to use a subset of the MATLAB
programming language to write functions that
describe state machines and arithmetic operators.
Functions written in this way can be attached to
blocks in System Generator and can be automatically
compiled into equivalent HDL.
Importing a System Generator
Design into a Bigger System
Discusses how to take the VHDL netlist from a System
Generator design and synthesize it in order to embed
it into a larger design. Also shows how VHDL created
by System Generator can be incorporated into a
simulation model of the overall system.
Configurable Subsystems and
System Generator
Explains how to use configurable subsystems in
System Generator. Describes common tasks such as
defining configurable subsystems, deleting and
adding blocks, and using configurable subsystems to
import compilation results into System Generator
designs.
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Chapter 1: Hardware Design Using System Generator
Notes for Higher Performance
FPGA Design
Suggests design practices in System Generator that
lead to an efficient and high-performance
implementation in an FPGA.
Processing a System Generator
Design with FPGA Physical
Design Tools
Describes how to take the low-level HDL produced by
System Generator and use it in tools like Xilinx's
Project Navigator, ModelSim, and Synplicity's
Synplify.
Resetting Auto-Generated Clock
Enable Logic
Describes the behavior of rate changing blocks from
the System Generator library when the ce_clr signal
is used for re-synchronization.
Design Styles for the DSP48
Describes three ways to implement and configure a
DSP48 (Xtreme DSP Slice) in System Generator
Using FDATool in Digital Filter
Applications
Demonstrates one way to specify, implement and
simulate a FIR filter using the FDATool block.
Generating Multiple Cycle-True
Islands for Distinct Clocks
Describes how to implement multi-clock designs in
System Generator
Using ChipScope Pro Analyzer
for Real-Time Hardware
Debugging
Demonstrated how to connect and use the Xilinx
Debug Tool called ChipScope Pro within System
Generator
A Brief Introduction to FPGAs
A field programmable gate array (FPGA) is a general-purpose integrated circuit that is
“programmed” by the designer rather than the device manufacturer. Unlike an
application-specific integrated circuit (ASIC), which can perform a similar function in an
electronic system, an FPGA can be reprogrammed, even after it has been deployed into a
system.
An FPGA is programmed by downloading a configuration program called a bitstream into
static on-chip random-access memory. Much like the object code for a microprocessor, this
bitstream is the product of compilation tools that translate the high-level abstractions
produced by a designer into something equivalent but low-level and executable. Xilinx
System Generator pioneered the idea of compiling an FPGA program from a high-level
Simulink model.
An FPGA provides you with a two-dimensional array of configurable resources that can
implement a wide range of arithmetic and logic functions. These resources include
dedicated DSP blocks, multipliers, dual port memories, lookup tables (LUTs), registers, tristate buffers, multiplexers, and digital clock managers. In addition, Xilinx FPGAs contain
sophisticated I/O mechanisms that can handle a wide range of bandwidth and voltage
requirements. The Virtex-4 and Virtex-II Pro family FPGAs include embedded
microcontrollers (IBM PowerPC 405), and multi-gigabit serial transceivers. The compute
and I/O resources are linked under the control of the bitstream by a programmable
interconnect architecture that allows them to be wired together into systems.
FPGAs are high performance data processing devices. DSP performance is derived from
the FPGA’s ability to construct highly parallel architectures for processing data. In contrast
with a microprocessor or DSP processor, where performance is tied to the clock rate at
which the processor can run, FPGA performance is tied to the amount of parallelism that
can be brought to bear in the algorithms that make up a signal processing system. A
combination of increasingly high system clock rates (current system frequencies of 100-200
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A Brief Introduction to FPGAs
MHz are common today) and a highly-distributed memory architecture gives the system
designer an ability to exploit parallelism in DSP (and other) applications that operate on
data streams. For example, the raw memory bandwidth of a large FPGA running at a clock
rate of 150 MHz can be hundreds of terabytes per second.
There are many DSP applications (e.g., digital up/down converters) that can be
implemented only in custom integrated circuits (ICs) or in an FPGA; a von Neumann
processor lacks both the compute capability and the memory bandwidth required.
Advantages of using an FPGA include significantly lower non-recurring engineering costs
than those associated with a custom IC (FPGAs are commercial off-the-shelf devices),
shorter time to market, and the configurability of an FPGA, which allows a design to be
modified, even after deployment in an end application.
When working in System Generator, it is important to keep in mind that an FPGA has
many degrees of freedom in implementing signal processing functions. You have, for
example, the freedom to define data path widths throughout your system and to employ
many individual data processors (e.g., multiply-accumulate engines), depending on
system requirements. System Generator provides abstractions that allow you to design for
an FPGA largely by thinking about the algorithm you want to implement. However, the
more you know about the underlying FPGA, the more likely you are to exploit the unique
capabilities an FPGA provides in achieving high performance.
The remainder of this topic is a brief introduction to some of the logic resources available in
the FPGA, so that you gain some appreciation for the abstractions provided in System
Generator.
The figure above shows a physical view of a Virtex-4 FPGA. To a signal DSP engineer, an
FPGA can be thought of as a 2-D array of logic slices striped with columns of hard macro
blocks (block memory and arithmetic blocks) suitable for implementing DSP functions,
embedded within a configurable interconnect mesh. In a Virtex-4 FPGA, the DSP blocks
(shown in the next figure) can run in excess of 450 MHz, and are pitch-matched to dual
port memory blocks (BRAMs) whose ports can be configured to a wide range of word sizes
(18 Kb total per BRAM). The Virtex-4 SX55 device contains 512 such DSP blocks and
BRAMs. In System Generator, you can access all of these resources through arithmetic and
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Chapter 1: Hardware Design Using System Generator
logic abstractions to build very high performance digital filters, FFTs, and other arithmetic
and signal processing functions.
While the multiply-accumulate function supported by a Virtex-4 DSP block is familiar to a
DSP engineer, it is instructive to take a closer look at the Virtex family logic slice (shown
below), which is the fundamental unit of the logic fabric array.
Each logic slice contains two 4-input lookup tables (LUTs), two configurable D-flip flops,
multiplexers, dedicated carry logic, and gates used for creating slice-based multipliers.
Each LUT can implement an arbitrary 4-input Boolean function. Coupled with dedicated
logic for implementing fast carry circuits, the LUTs can also be used to build fast
adder/subtractors and multipliers of essentially any word size. In addition to
implementing Boolean functions, each LUT can also be configured as a 16x1 bit RAM or as
a shift register (SRL16). An SRL16 shift register is a synchronously clocked 16x1 bit delay
line with a dynamically addressable tap point.
In System Generator, these different memory options are represented with higher-level
abstractions. Instead of providing a D-flip flop primitive, System Generator provides a
register of arbitrary size. There are two blocks that provide abstractions of arbitrary
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A Brief Introduction to FPGAs
width, arbitrary depth delay lines that map directly onto the SRL16 configuration. The
delay block can be used for pipeline balancing, and can also be used as storage for timedivision multiplexed (TDM) data streams. The addressable shift register (ASR) block,
with a function depicted in the figure below, provides an arbitrary width, arbitrary depth
tapped delay line. This block is of particular interest to the DSP engineer, since it can be
used to implement tapped delay lines as well as sweeping through TDM data streams.
Although random access memories can be constructed either out of the BRAM or LUT
(RAM16x1) primitives, doing so can require considerable care to ensure most efficient
mappings, and considerable clerical attention to detail to correctly assemble the primitives
into larger structures. System Generator removes the need for such tasks.
For example, the dual port RAM (DPRAM) block shown in the figure below maps
efficiently onto as many BRAM or RAM16x1 components on the device as are necessary to
implement the desired memory. As can be seen from the mask dialog box for the DPRAM,
the interface allows you to specify a type of memory (BRAM or RAM16x1), depth (data
width is inferred from the Simulink signal driving a particular input port), initial memory
contents, and other characteristics.
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In general, System Generator maps abstractions onto device primitives efficiently, freeing
you from worrying about interconnections between the primitives. System Generator
employs libraries of intellectual property (IP) when appropriate to provide efficient
implementations of functions in the block libraries. In this way, you don’t always have to
have detailed knowledge of the underlying FPGA details. However, when it makes sense
to implement an algorithm using basic functions (e.g., adder, register, memory), System
Generator allows you to exploit your FPGA knowledge while reducing the clerical tasks of
managing all signals explicitly.
System Generator library blocks and the mapping from Simulink to hardware are
described in detail in subsequent topics of this documentation. There is a wealth of
detailed information about FPGAs that can be found online at http://support.xilinx.com,
including data books, application notes, white papers, and technical articles.
Note to the DSP Engineer
System Generator extends Simulink to enable hardware design, providing high-level
abstractions that can be automatically compiled into an FPGA. Although the arithmetic
abstractions are suitable to Simulink (discrete time and space dynamical system
simulation), System Generator also provides access to features in the underlying FPGA.
The more you know about a hardware realization (e.g., how to exploit parallelism and
pipelining), the better the implementation you’ll obtain. Using IP cores makes it possible to
have efficient FPGA designs that including complex functions like FFTs. System Generator
also makes it possible to refine a model to more accurately fit the application.
Scattered throughout the System Generator documentation are notes that explain ways in
which system parameters can be used to exploit hardware capabilities.
Note to the Hardware Engineer
System Generator does not replace hardware description language (HDL)-based design,
but does makes it possible to focus your attention only on the critical parts. By analogy,
most DSP programmers do not program exclusively in assembler; they start in a higherlevel language like C, and write assembly code only where it is required to meet
performance requirements.
A good rule of thumb is this: in the parts of the design where you must manage internal
hardware clocks (e.g., using the DDR or phased clocking), you should implement using
HDL. The less critical portions of the design can be implemented in System Generator, and
then the HDL and System Generator portions can be connected. Usually, most portions of
a signal processing system do not need this level of control, except at external interfaces.
System Generator provides mechanisms to import HDL code into a design (see Importing
HDL Modules) that are of particular interest to the HDL designer.
Another aspect of System Generator that is of interest to the engineer who designs using
HDL is its ability automatically generate an HDL testbench, including test vectors. This
aspect is described in the topic HDL Testbench.
Finally, the hardware co-simulation interfaces described in the topic Using Hardware CoSimulation allow you to run a design in hardware under the control of Simulink, bringing
the full power of MATLAB and Simulink to bear for data analysis and visualization.
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Design Flows using System Generator
Design Flows using System Generator
System Generator can be useful in many settings. Sometimes you may want to explore an
algorithm without translating the design into hardware. Other times you might plan to use
a System Generator design as part of something bigger. A third possibility is that a System
Generator design is complete in its own right, and is to be used in FPGA hardware. This
topic describes all three possibilities.
Algorithm Exploration
System Generator is particularly useful for algorithm exploration, design prototyping, and
model analysis. When these are the goals, you can use the tool to flesh out an algorithm in
order to get a feel for the design problems that are likely to be faced, and perhaps to
estimate the cost and performance of an implementation in hardware. The work is
preparatory, and there is little need to translate the design into hardware.
In this setting, you assemble key portions of the design without worrying about fine points
or detailed implementation. Simulink blocks and MATLAB M-code provide stimuli for
simulations, and for analyzing results. Resource estimation gives a rough idea of the cost
of the design in hardware. Experiments using hardware generation can suggest the
hardware speeds that are possible.
Once a promising approach has been identified, the design can be fleshed out. System
Generator allows refinements to be done in steps, so some portions of the design can be
made ready for implementation in hardware, while others remain high-level and abstract.
System Generator's facilities for hardware co-simulation are particularly useful when
portions of a design are being refined.
Implementing Part of a Larger Design
Often System Generator is used to implement a portion of a larger design. For example,
System Generator is a good setting in which to implement data paths and control, but is
less well suited for sophisticated external interfaces that have strict timing requirements. In
this case, it may be useful to implement parts of the design using System Generator,
implement other parts outside, and then combine the parts into a working whole.
A typical approach to this flow is to create an HDL wrapper that represents the entire
design, and to use the System Generator portion as a component. The non-System
Generator portions of the design can also be components in the wrapper, or can be
instantiated directly in the wrapper.
Implementing a Complete Design
Many times, everything needed for a design is available inside System Generator. For such
a design, pressing the Generate button instructs System Generator to translate the design
into HDL, and to write the files needed to process the HDL using downstream tools. The
files written include the following:
•
HDL that implements the design itself;
•
A clock wrapper that encloses the design. This clock wrapper produces the clock and
clock enable signals that the design needs.
•
A HDL testbench that encloses the clock wrapper. The testbench allows results from
Simulink simulations to be compared against ones produced by a logic simulator.
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•
Project files and scripts that allow various synthesis tools, such as XST and Synplify
Pro to operate on System Generator HDL
•
Files that allow the System Generator HDL to be used as a project in Project
Navigator.
For details concerning the files that System Generator writes, see the topic Compilation
Results.
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System-Level Modeling in System Generator
System-Level Modeling in System Generator
System Generator allows device-specific hardware designs to be constructed directly in a
flexible high-level system modeling environment. In a System Generator design, signals
are not just bits. They can be signed and unsigned fixed-point numbers, and changes to the
design automatically translate into appropriate changes in signal types. Blocks are not just
stand-ins for hardware. They respond to their surroundings, automatically adjusting the
results they produce and the hardware they become.
System Generator allows designs to be composed from a variety of ingredients. Data flow
models, traditional hardware design languages (VHDL, Verilog, and EDIF), and functions
derived from the MATLAB programming language, can be used side-by-side, simulated
together, and synthesized into working hardware. System Generator simulation results are
bit and cycle-accurate. This means results seen in simulation exactly match the results that
are seen in hardware. System Generator simulations are considerably faster than those
from traditional HDL simulators, and results are easier to analyze.
System Generator Blocksets
Describes how System Generator's blocks are
organized in libraries, and how the blocks can be
parameterized and used.
Signal Types
Describes the data types used by System Generator
and ways in which data types can be automatically
assigned by the tool.
Bit-True and Cycle-True
Modeling
Specifies the relationship between the Simulink-based
simulation of a System Generator model and the
behavior of the hardware that can be generated from
it.
Timing and Clocking
Describes how clocks are implemented in hardware,
and how their implementation is controlled inside
System Generator. Explains how System Generator
translates a multirate Simulink model into working
clock-synchronous hardware.
Synchronization Mechanisms
Describes mechanisms that can be used to
synchronize data flow across the data path elements
in a high-level System Generator design, and
describes how control path functions can be
implemented.
Block Masks and Parameter
Passing
Explains how parameterized systems and subsystems
are created in Simulink.
Resource Estimation
Describes how to generate estimates of the hardware
needed to implement a System Generator design.
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System Generator Blocksets
A Simulink blockset is a library of blocks that can be connected in the Simulink block editor
to create functional models of a dynamical system. For system modeling, System
Generator blocksets are used like other Simulink blocksets. The blocks provide
abstractions of mathematical, logic, memory, and DSP functions that can be used to build
sophisticated signal processing (and other) systems. There are also blocks that provide
interfaces to other software tools (e.g., FDATool, ModelSim) as well as the System
Generator code generation software.
System Generator blocks are bit-accurate and cycle-accurate. Bit-accurate blocks produce
values in Simulink that match corresponding values produced in hardware; cycle-accurate
blocks produce corresponding values at corresponding times.
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Xilinx Blockset
The Xilinx Blockset is a family of libraries that contain basic System Generator blocks.
Some blocks are low-level, providing access to device-specific hardware. Others are highlevel, implementing (for example) signal processing and advanced communications
algorithms. For convenience, blocks with broad applicability (e.g., the Gateway I/O
blocks) are members of several libraries. Every block is contained in the Index library. The
libraries are described below.
Library
Description
Index
Every block in the Xilinx Blockset.
Basic Elements
ElementsStandard building blocks for digital logic
Communication
Forward error correction and modulator blocks, commonly used in
digital communications systems
Control Logic
Blocks for control circuitry and state machines
Data Types
Blocks that convert data types (includes gateways)
DSP
Digital signal processing (DSP) blocks
Math
Blocks that implement mathematical functions
Memory
Blocks that implement and access memories
Shared Memory
Blocks that implement and access Xilinx shared memories
Tools
“Utility” blocks, e.g., code generation (System Generator block),
resource estimation, HDL co-simulation, etc
Note: More information concerning blocks can be found in the topic Xilinx Blockset.
Xilinx Reference Blockset
The Xilinx Reference Blockset contains composite System Generator blocks that implement
a wide range of functions. Blocks in this blockset are organized by function into different
libraries. The libraries are described below.
Library
Description
Communication
Blocks commonly used in digital communications systems
Control Logic
LogicBlocks used for control circuitry and state machines
DSP
Digital signal processing (DSP) blocks
Imaging
Image processing blocks
Math
Blocks that implement mathematical functions
Each block in this blockset is a composite, i.e., is implemented as a masked subsystem, with
parameters that configure the block.
You can use blocks from the Reference Blockset libraries as is, or as starting points when
constructing designs that have similar characteristics. Each reference block has a
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description of its implementation and hardware resource requirements. Individual
documentation for each block is also provided in the topic Xilinx Reference Blockset.
Signal Types
In order to provide bit-accurate simulation of hardware, System Generator blocks operate
on Boolean and arbitrary precision fixed-point values. By contrast, the fundamental scalar
signal type in Simulink is double precision floating point. The connection between Xilinx
blocks and non-Xilinx blocks is provided by gateway blocks. The gateway in converts a
double precision signal into a Xilinx signal, and the gateway out converts a Xilinx signal into
double precision. Simulink continuous time signals must be sampled by the Gateway In
block.
Most Xilinx blocks are polymorphic, i.e., they are able to deduce appropriate output types
based on their input types. When full precision is specified for a block in its parameters
dialog box, System Generator chooses the output type to ensure no precision is lost. Sign
extension and zero padding occur automatically as necessary. User-specified precision is
usually also available. This allows you to set the output type for a block and to specify how
quantization and overflow should be handled. Quantization possibilities include unbiased
rounding towards plus or minus infinity, depending on sign, or truncation. Overflow
options include saturation, truncation, and reporting overflow as an error.
Note: System Generator data types can be displayed by selecting Format > Port Data Types in
Simulink. Displaying data types makes it easy to determine precision throughout a model. If, for
example, the type for a port is Fix_11_9, then the signal is a two's complement signed 11-bit number
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having nine fractional bits. Similarly, if the type is Ufix_5_3, then the signal is an unsigned 5-bit
number having three fractional bits.
In the System Generator portion of a Simulink model, every signal must be sampled.
Sample times may be inherited using Simulink's propagation rules, or set explicitly in a
block customization dialog box. When there are feedback loops, System Generator is
sometimes unable to deduce sample periods and/or signal types, in which case the tool
issues an error message. Assert blocks must be inserted into loops to address this problem.
It is not necessary to add assert blocks at every point in a loop; usually it suffices to add an
assert block at one point to “break” the loop.
Note: Simulink can display a model by shading blocks and signals that run at different rates with
different colors (Format > Sample Time Colors in the Simulink pulldown menus). This is often useful
in understanding multirate designs
Bit-True and Cycle-True Modeling
Simulations in System Generator are bit-true and cycle-true. To say a simulation is bit-true
means that at the boundaries (i.e., interfaces between System Generator blocks and nonSystem Generator blocks), a value produced in simulation is bit-for-bit identical to the
corresponding value produced in hardware. To say a simulation is cycle-true means that at
the boundaries, corresponding values are produced at corresponding times. The
boundaries of the design are the points at which System Generator gateway blocks exist.
When a design is translated into hardware, Gateway In (respectively, Gateway Out) blocks
become top-level input (resp., output) ports.
Timing and Clocking
Discrete Time Systems
Designs in System Generator are discrete time systems. In other words, the signals and the
blocks that produce them have associated sample rates. A block’s sample rate determines
how often the block is awoken (allowing its state to be updated). System Generator sets
most sample rates automatically. A few blocks, however, set sample rates explicitly or
implicitly.
Note: For an in-depth explanation of Simulink discrete time systems and sample times, consult the
Using Simulink reference manual from the MathWorks, Inc.
A simple System Generator model illustrates the behavior of discrete time systems.
Consider the model shown below. It contains a gateway that is driven by a Simulink source
(Sine Wave), and a second gateway that drives a Simulink sink (Scope).
The Gateway In block is configured with a sample period of one second. The Gateway Out
block converts the Xilinx fixed-point signal back to a double (so it can analyzed in the
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Simulink scope), but does not alter sample rates. The scope output below shows the
unaltered and sampled versions of the sine wave.
Multirate Models
System Generator supports multirate designs, i.e., designs having signals running at
several sample rates. System Generator automatically compiles multirate models into
hardware. This allows multirate designs to be implemented in a way that is both natural
and straightforward in Simulink.
Rate-Changing Blocks
System Generator includes blocks that change sample rates. The most basic rate changers
are the Up Sample and Down Sample blocks. As shown in the figure below, these blocks
explicitly change the rate of a signal by a fixed multiple that is specified in the block’s
dialog box.
Other blocks (e.g., the Parallel To Serial and Serial To Parallel converters) change rates
implicitly in a way determined by block parameterization.
Consider the simple multirate example below. This model has two sample periods, SP1
and SP2. The Gateway In dialog box defines the sample period SP1. The Down Sample
block causes a rate change in the model, creating a new rate SP2 which is half as fast as SP1.
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Hardware Oversampling
Some System Generator blocks are oversampled, i.e., their internal processing is done at a
rate that is faster than their data rates. In hardware, this means that the block requires more
than one clock cycle to process a data sample. In Simulink such blocks do not have an
observable effect on sample rates.
One block that can be oversampled is the DAFIR FIR filter. An oversampled DAFIR
processes samples serially, thus running at a higher rate, but using less hardware.
Although blocks that are oversampled do not cause an explicit sample rate change in
Simulink, System Generator considers the internal block rate along with all other sample
rates when generating clocking logic for the hardware implementation. This means that
you must consider the internal processing rates of oversampled blocks when you specify
the Simulink system period value in the System Generator block dialog box.
Asynchronous Clocking
System Generator focuses on the design of hardware that is synchronous to a single clock.
It can, under some circumstances, be used to design systems that contain more than one
clock. This is possible provided the design can be partitioned into individual clock
domains with the exchange of information between domains being regulated by dual port
memories and FIFOs. System Generator fully supports such multi-clock designs, including
the ability to simulate them in Simulink and to generate complete hardware descriptions.
Details are discussed in the topic Generating Multiple Cycle-True Islands for Distinct
Clocks. The remainder of this topic focuses exclusively on the clock-synchronous aspects
of System Generator. This discussion is relevant to both single-clock and multiple-clock
designs.
Synchronous Clocking
As shown in the figure below, when you use the System Generator token to compile a
design into hardware, there are three clocking options for Multirate implementation: (1)
Clock Enables (the default), (2) Clock Generator(DCM), and (3) Expose Clock Ports.
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The Clock Enables Option
When System Generator compiles a model into hardware with the Clock Enable option
selected, System Generator preserves the sample rate information of the design in such a
way that corresponding portions in hardware run at appropriate rates. In hardware,
System Generator generates related rates by using a single clock in conjunction with clock
enables, one enable per rate. The period of each clock enable is an integer multiple of the
period of the system clock.
Inside Simulink, neither clocks nor clock enables are required as explicit signals in a
System Generator design. When System Generator compiles a design into hardware, it
uses the sample rates in the design to deduce what clock enables are needed. To do this, it
employs two user-specified values from the System Generator block: the Simulink system
period and FPGA clock period. These numbers define the scaling factor between time in a
Simulink simulation, and time in the actual hardware implementation. The Simulink
system period must be the greatest common divisor (gcd) of the sample periods that
appear in the model, and the FPGA clock period is the period, in nanoseconds, of the
system clock. If p represents the Simulink system period, and c represents the FPGA
system clock period, then something that takes kp units of time in Simulink takes k ticks of
the system clock (hence kc nanoseconds) in hardware.
To illustrate this point, consider a model that has three Simulink sample periods 2, 3, and
4. The gcd of these sample periods is 1, and should be specified as such in the Simulink
System Period field for the model. Assume the FPGA Clock Period is specified to be 10ns.
With this information, the corresponding clock enable periods can be determined in
hardware.
In hardware, we refer to the clock enables corresponding to the Simulink sample periods 2,
3, and 4 as CE2, CE3, and CE4, respectively. The relationship of each clock enable period to
the system clock period can be determined by dividing the corresponding Simulink
sample period by the Simulink System Period value. Thus, the periods for CE2, CE3, and
CE4 equal 2, 3, and 4 system clock periods, respectively. A timing diagram for the example
clock enable signals is shown below:
The Clock Generator(DCM) Option
If the implementation target is an FPGA with a Digital Clock Manager (DCM), you can
choose to drive the clock tree with a DCM. The DCM option is desirable when high fanout
on clock enable nets make it difficult to achieve timing closure.
System Generator instantiates the DCM in a top-level HDL clock wrapper and configures
the DCM to provide up to three clock ports at different rates for Virtex-4 and Virtex-5 and up
to two clock ports for Spartan-3A DSP. If this DCM option is selected and the set of rates in
the design cannot be supported using a single DCM, than an error will be issued. The
mapping of rates to the DCM outputs is done according to the following priority scheme:
CLK0 > CLK2x > CLKdv > CLKfx.
A dcm_reset input port is exposed on the top-level wrapper to allow the external design
to reset the DCM after bitstream configuration. A dcm_locked output port is also exposed
to help the external design synchronize the input data with the single clk input port.
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Known Limitations: The following System Generator blocks are not supported by the
Clock Generator(DCM) Option:
•
Clock Enable Probe
•
Clock Probe
•
DAFIR
•
Downsample - when the Sample option First value of the frame is selected
•
FIR Compiler - when the core rate is not equal to the input sample rate
•
Parallel to Serial- when the Latency option is specified as 0 (zero)
•
Time Division De-Multiplexer
•
Time Division Multiplexer
•
Upsample - when the Copy samples (otherwise zeros are inserted) option is not
selected.
Note: For Release 10.1, the Clock Generator(DCM) option was tested in hardware using Virtex 4
and Virtex 5 platforms at 400MHz and the Spartan-3A DSP platform at 190MHz.
The Expose Clock Ports Option
When you select this option, System Generator creates a top-level wrapper that exposes a
clock port for each rate. You can then manually instantiate a clock generator outside the
design to drive the clock ports.
Tutorial Example: Using the Clock Generator(DCM) Option
The following step-by-step example will show you how to select the Clock Generator
(DCM) option, netlist the HDL design, implement the design in ISE, simulate the design
and examine the files and reports to verify that the DCM is properly instantiated and
configured.
The dcm_case1 design example is located at the following pathname
<sysgen_tree>/examples/clocking_options/dcm_case1/dcm_case1.mdl
1.
Open the model in MATLAB and observe the following blocks:
•
Addressable Shift Register (ASR): used to implement the input delay buffer. The
address port runs n times faster than the data port, where n is the number of the filter
taps (5 for this example)
•
Coefficient ROM: used to store the filter coefficients
•
Counter: used to generate addresses for the ROM and ASR
•
Comparator: used to generate the reset and enable signals
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•
MAC Engine: used as a Multiply-Accumulator operator for the filter
2.
Double-click on the System Generator token to bring up the following dialog box:
As shown above, select Clock Generator(DCM), then click Generate. After a few
moments, a sub-directory named hdl_netlist is created in the current working directory
containing the generated files.
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3.
In the MATLAB Current Directory window, double-click on the file
dcm_case1_sysgen.log. As shown below, the clocks from the DCM are listed.
4.
Launch ISE, then load the ISE project at pathname
./hdl_netlist/dcm_case1_dcm_mcw.ise
5.
Under the Project Navigator Processes tab, double-click on Implement Design.
6.
From the Project Navigator Sources tab, do the following:
a.
Double-click on the file dcm_case1_dcm_mcw.vhd, then scroll down to view the
DCM component declaration as shown below by the VHDL code snippet:
b.
Observe that System Generator automatically infers and instantiates the DCM
instance and its parameters according to the required clock outputs.
c.
Close the VHDL file.
Next, you are going to examine the clock propagation by examining the ISE timing report.
To be able to see the DCM clock outputs in the ISE timing report, you must first create a
simple user constraint file (UCF).
7.
Under the Processes tab > User Constraints, double-click on Create Timing
Constraints. Constrain the design as shown in the figure below, then save the file.
8.
Examine the DCM clock outputs: Under Processes tab > Implement Design > Place &
Route > Generate Post-Place & Route Static Timing
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9.
Once finished, double -click on Analyze Post-Place & Route Static Timing and you
should see the information in the figure below:
The timing report validates the correct clock propagation by System Generator - 10 ns
and 50 ns.
Next you want to perform a behavior simulation using the ModelSim.
10. As shown in the following figure, move to the Sources for dialog box in the Sources
window, then select Behavioral Simulation
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Note: System Generator automatically creates the top-wrapper VHDL testbench, script file and
input/output stimulus data files. The Processes tab changes and displays according to the
Sources type being selected.
1. Select
2. Double Click
11. Simulate the design, as shown above, by double-click on Simulate Behavioral Model
in the Processes window
12. After the simulation is finished, you should be able to observe the simulation
waveforms as shown in the figure below:
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Summary
When you select the Clock Generator(DCM) option, System Generator automatically
infers and instantiates a DCM without further manual intervention. You do not have to set
attributes or specify DCM clock outputs. Clock rates are determined by the same
methodology when you use the Clock Enables option. You should expect minimal clock
skew when selecting the Clock Generator (DCM) option compared to the Clock Enables
option.
Tutorial Example: Using the Expose Clock Ports Option
The following step-by-step example will show you how to select the Expose Clock Ports
option, netlist the HDL design, implement the design in ISE, simulate the design, then
examine the files and reports to verify the design.
The expose_clock_ports_case1 design example is located at the following pathname
<sysgen_tree>/examples/clocking_options/expose_clock_ports_case1/e
xpose_clock_ports_case1.mdl
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1.
Open the model in MATLAB and observe the following blocks:
•
Addressable Shift Register (ASR): used to implement the input delay buffer. The
address port runs n times faster than the data port, where n is the number of the filter
taps (5 for this example)
•
Coefficient ROM: used to store the filter coefficients
•
Counter: used to generate addresses for the ROM and ASR
•
Comparator: used to generate the reset and enable signals
•
MAC Engine: used as a Multiply-Accumulator operator for the filter
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2.
Double-click on the System Generator token to bring up the following dialog box:
As shown above, select Expose Clock Ports, then click Generate. After a few moments, a
sub-directory named hdl_netlist is created in the current working directory containing the
generated files.
3.
Launch ISE, then load the ISE project at pathname
./hdl_netlist/expose_clock_ports_case1_mcw.ise
4.
Under the Project Navigator Processes tab, double-click on Implement Design.
5.
From the Project Navigator Sources tab, do the following:
a.
double-click on the file expost_clock_ports_case1_mcw.vhd, then scroll
down to view the entity named expose_clock_ports_mcw, as shown below:
b. Observe that System Generator infers the clocks based on the different rates in the
design and brings the clock ports to the top-level wrapper. Since this design
contains two clock rates, clocks clk_1 and clk_5 are pulled to the top-level
wrapper. This will allow you to directly drive the multiple synchronous clocks
from outside the System Generator design.
c.
Close the VHDL file.
Next you want to perform a behavior simulation using the ModelSim.
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6.
As shown below, move to the Sources for dialog box in the Sources window, then
select Behavioral Simulation
Note: System Generator automatically creates the top-wrapper VHDL testbench, script file and
input/output stimulus data files. The Processes tab changes and displays according to the
Sources type being selected.
1. Select
2. Double Click
7.
Simulate the design, as shown above, by double-click on Simulate Behavioral Model
in the Processes window
8.
After the simulation is finished, you should be able to observe the simulation
waveforms as shown in the figure below:
Summary
When you select the Expose Clock Ports option, System Generator automatically infers the
correct clocks from the design rates and exposes the clock ports in the top-level wrapper.
The clock rates are determined by the same methodology when you use the Clock Enables
option. You can now drive the exposed clock ports from an external synchronous clock
source.
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Synchronization Mechanisms
System Generator does not make implicit synchronization mechanisms available. Instead,
synchronization is the responsibility of the designer, and must be done explicitly.
Valid Ports
System Generator provides several blocks (in particular, a FIFO) that can be used for
synchronization. Several blocks provide input (respectively, output) ports that specify
when an input (resp., output) sample is valid. Such ports can be chained, affording a
primitive form of flow control. Blocks with such ports include the FFT, FIR, and Viterbi.
Indeterminate Data
Indeterminate values are common in many hardware simulation environments. Often they
are called “don’t cares” or “Xs”. In particular, values in System Generator simulations can
be indeterminate. A dual port memory block, for example, can produce indeterminate
results if both ports of the memory attempt to write the same address simultaneously.
What actually happens in hardware depends upon effectively random implementation
details that determine which port sees the clock edge first. Allowing values to become
indeterminate gives the system designer greater flexibility. Continuing the example, there
is nothing wrong with writing to memory in an indeterminate fashion if subsequent
processing does not rely on the indeterminate result.
HDL modules that are brought into the simulation through HDL co-simulation are a
common source for indeterminate data samples. System Generator presents indeterminate
values to the inputs of an HDL co-simulating module as the standard logic vector 'XXX . .
. XX'.
Indeterminate values that drive a Gateway Out become what are called NaNs. (NaN
abbreviates “not a number”.) In a Simulink scope, NaN values are not plotted. Conversely,
NaNs that drive a Gateway In become indeterminate values. System Generator provides
an Indeterminate Probe block that allows for the detection of indeterminate values. This
probe cannot be translated into hardware.
In System Generator, any arithmetic signal can be indeterminate, but Boolean signals
cannot be. If a simulation reaches a condition that would force a Boolean to become
indeterminate, the simulation is halted and an error is reported. Many Xilinx blocks have
control ports that only allow Boolean signals as inputs. The rule concerning indeterminate
Booleans means that such blocks never see an indeterminate on a control port
A UFix_1_0 is a type that is equivalent to Boolean except for the above restriction
concerning indeterminate data.
Block Masks and Parameter Passing
The same scoping and parameter passing rules that apply to ordinary Simulink blocks
apply to System Generator blocks. Consequently, blocks in the Xilinx Blockset can be
parameterized using MATLAB variables and expressions. This capability makes possible
highly parametric designs that take advantage of the expressive and computational power
of the MATLAB language.
Block Masks
In Simulink, blocks are parameterized through a mechanism called masking. In essence, a
block can be assigned mask variables whose values can be specified by a user through dialog
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box prompts or can be calculated in mask initialization commands. Variables are stored in
a mask workspace. A mask workspace is local to the blocks under the mask and cannot be
accessed by external blocks.
Note: It is possible for a mask to access global variables and variables in the base workspace. To
access a base workspace variable, use the MATLAB evalin function. For more information on the
MATLAB and Simulink scoping rules, refer to the manuals titled Using MATLAB and Using Simulink
from The Mathworks, Inc.
Parameter Passing
It is often desirable to pass variables to blocks inside a masked subsystem. Doing so allows
the block’s configuration to be determined by parameters on the enclosing subsystem. This
technique can be applied to parameters on blocks in the Xilinx blockset whose values are
set using a listbox, radio button, or checkbox. For example, when building a subsystem
that consists of a multiply and accumulate block, you can create a parameter on the
subsystem that allows you to specify whether to truncate or round the result. This
parameter will be called trunc_round as shown in the figure below.
As shown below, in the parameter editing dialog for the accumulator and multiplier
blocks, there are radio buttons that allow either the truncate or round option to be selected.
In order to use a parameter rather than the radio button selection, right click on the radio
button and select: “Define With Expression”. A MATLAB expression can then be used as
the parameter setting. In the example below, the trunc_round parameter from the
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subsystem mask can be used in both the accumulator and multiply blocks so that each
block will use the same setting from the mask variable on the subsystem.
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Resource Estimation
System Generator supplies tools that estimate the FPGA hardware resources needed to
implement a design. Estimates include numbers of slices, lookup tables, flip-flops, block
memories, embedded multipliers, I/O blocks and tristate buffers. These estimates make it
easy to determine how design choices affect hardware requirements. To estimate the
resources needed for a subsystem, drag a Resource Estimator block into the subsystem,
double-click on the estimator, and press the Estimate button.
Automatic Code Generation
System Generator automatically compiles designs into low-level representations. The
ways in which System Generator compiles a model can vary, and depend on settings in the
System Generator block. In addition to producing HDL descriptions of hardware, the tool
generates auxiliary files. Some files (e.g., project files, constraints files) assist downstream
tools, while others (e.g., VHDL testbench) are used for design verification.
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Compiling and Simulating Using
the System Generator Block
Describes how to use the System Generator block to
compile designs into equivalent low-level HDL.
Compilation Results
Describes the low-level files System Generator
produces when HDL Netlist is selected on the System
Generator block and Generate is pushed.
HDL Testbench
Describes the VHDL testbench that System Generator
can produce.
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Compiling and Simulating Using the System Generator Block
System Generator automatically compiles designs into low-level representations. Designs
are compiled and simulated using the System Generator block. This topic describes how to
use the block.
Before a System Generator design can be simulated or translated into hardware, the design
must include a System Generator block. When creating a new design, it is a good idea to
add a System Generator block immediately. The System Generator block is a member of
the Xilinx Blockset’s Basic Elements and Tools libraries. As with all Xilinx blocks, the
System Generator block can also be found in the Index library.
A design must contain at least one System Generator block, but can contain several System
Generator blocks on different levels (one per level). A System Generator block that is
underneath another in the hierarchy is a slave; one that is not a slave is a master. The scope
of a System Generator block consists of the level of hierarchy into which it is embedded
and all subsystems below that level. Certain parameters (e.g. Simulink System Period)
can be specified only in a master.
Once a System Generator block is added, it is possible to specify how code generation and
simulation should be handled. The block’s dialog box is shown below:
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Compilation Type and the Generate Button
Pressing the Generate button instructs System Generator to compile a portion of the
design into equivalent low-level results. The portion that is compiled is the sub-tree whose
root is the subsystem containing the block. (To compile the entire design, use a System
Generator block placed at the top of the design.) The compilation type (under
Compilation) specifies the type of result that should be produced. The possible types are
•
Two types of Netlists, HDL Netlist and NGC Netlist
•
Bitstream - produces an FPGA configuration bitstream that is ready to run in a
hardware FPGA platform
•
EDK Export Tool - for exporting to the Xilinx Embedded Development Kit various
varieties of hardware co-simulation, and
•
Timing Analysis - a report on the timing of the design.
HDL Netlist is the type used most often. In this case, the result is a collection of HDL and
EDIF files, and a few auxiliary files that simplify downstream processing. The collection is
ready to be processed by a synthesis tool (e.g., XST), and then fed to the Xilinx physical
design tools (i.e., ngdbuild, map, par, and bitgen) to produce a configuration bitstream for
a Xilinx FPGA. The files that are produced are described in more detail in Compilation
Results.
NGC Netlist is similar to HDL Netlist but the resulting files are NGC files instead of HDL
files.
When the type is a variety of hardware co-simulation, then System Generator produces an
FPGA configuration bitstream that is ready to run in a hardware FPGA platform. The
particular platform depends on the variety chosen. For example, when the variety is
Hardware Co-simulation > XtremeDSP Development Kit > PCI and USB, then the
bitstream is suitable for the XtremeDSP board (available for separate purchase from
Xilinx). System Generator also produces a hardware co-simulation block to which the
bitstream is associated. This block is able to participate in Simulink simulations. It is
functionally equivalent to the portion of the design from which it was derived, but is
implemented by its bitstream. In a simulation, the block delivers the same results as those
produced by the portion, but the results are calculated in working hardware.
Note: It is possible to customize the list of compilation types. See the topic Hardware Co-Simulation
Installation for details.
The remaining compilation parameters are described in the table below. Some are
available only when the compilation type is HDL Netlist. For example, the clock pin
location cannot be chosen for a hardware co-simulation compilation because it is fixed in
each hardware FPGA platform.
Control
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Description
Part
Defines the FPGA part to be used.
Target Directory
Defines where System Generator should write compilation results.
Because System Generator and the FPGA physical design tools
typically create many files, it is best to create a separate target
directory, i.e., a directory other than the directory containing your
Simulink model files. The directory can be an absolute path (e.g.
c:\netlist) or a path relative to the directory containing the model
(e.g. netlist).
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Control
Description
Synthesis Tool
Specifies the tool to be used to synthesize the design. The
possibilities are Synplify, Synplify Pro and Xilinx XST.
Hardware Description
Language
Specifies the language to be used for HDL netlist of the design. The
possibilities are VHDL and Verilog.
Create Testbench
This instructs System Generator to create an HDL testbench.
Simulating the testbench in an HDL simulator compares Simulink
simulation results with ones obtained from the compiled version of
the design. To construct test vectors, System Generator simulates the
design in Simulink, and saves the values seen at gateways. The top
HDL file for the testbench is named <name>_testbench.vhd/.v,
where <name> is a name derived from the portion of the design
being tested and the extension is dependent on the hardware
description language.
Import as
Configurable
Tells System Generator to do two things: 1) Construct a block to
which the results of compilation are associated, and 2) Construct a
configurable subsystem consisting of the block and the original
subsystem from which the block was derived. See Configurable
Subsystems and System Generator for details.
FPGA Clock Period
Defines the period in nanoseconds of the hardware clock. The value
need not be an integer. The period is passed to the Xilinx
implementation tools through a constraints file, where it is used as
the global PERIOD constraint. Multicycle paths are constrained to
integer multiples of this value.
Clock Pin Location
Defines the pin location for the hardware clock. This information is
passed to the Xilinx implementation tools through a constraints file.
Multirate
implementation
Clock Enables (default): Creates a clock enable generator circuit to
drive a multirate design.
Clock Generator(DCM): Creates a clock wrapper with a DCM that
can drive up to three clock ports at different rates for Virtex-4 and
Virtex-5 and up to two clock ports for Spartan-3A DSP. The mapping
of rates to the DCM output ports is done using the following priority
scheme: CLK0 > CLK2x > CLKdv > CLKfx
Expose Clock Ports: This option exposes multiple clock ports on the
top-level of the System Generator design so you can apply multiple
synchronous clock inputs from outside the design.
Provide clock enable
clear pin
This instructs System Generator to provide a ce_clr port on the
top-level clock wrapper. The ce_clr signal is used to reset the
clock enable generation logic. Capability to reset clock enable
generations logic allows designs to have dynamic control for
specifying the beginning of data path sampling. See the topic for
details.
Simulink System Period
You must specify a value for Simulink System Period in the System Generator block
dialog box. This value tells the underlying rate, in seconds, at which simulations of the
design should run. The period must evenly divide all sample periods in the design. For
example, if the design consists of blocks whose sample periods are 2, 6, and 8, then the
largest acceptable sample period is 2, though other values such as 1 and 0.5 are also
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acceptable. Sample periods arise in three ways: some are specified explicitly, some are
calculated automatically, and some arise implicitly within blocks that involve internal rate
changes. For more information on how the system period setting affects the hardware
clock, refer to Timing and Clocking.
Before running a simulation or compiling the design, System Generator verifies that the
period evenly divides every sample period in the design. If a problem is found, System
Generator opens a dialog box suggesting an appropriate value. Clicking the button labeled
Update instructs System Generator to use the suggested value. To see a summary of period
conflicts, click the button labeled View Conflict Summary. If you allow System Generator
to update the period, you must restart the simulation or compilation.
It is possible to assemble a System Generator model that is inconsistent because its periods
cannot be reconciled. (For example, certain blocks require that they run at the system rate.
Driving an up-sampler with such a block produces an inconsistent model.) If, even after
updating the system period, System Generator reports there are conflicts, then the model is
inconsistent and must be corrected.
The period control is hierarchical; see the discussion of hierarchical controls below for
details.
Block Icon Display
The options on this control affect the display of the block icons on the model. After
compilation (which occurs when Generating, Simulating, or by pressing Control-D) of
the model various information about the block in your model can be displayed, depending
on which option is chosen.
•
Default—basic information about port directions are shown
•
Sample rates—the sample rates of each port are shown
•
Pipeline stages—the number of pipeline stages are shown
•
HDL port names—the names of the ports are shown
•
Input data types—the input data types for each port are shown
•
Output data types—output data types for each port are shown
Hierarchical Controls
The Simulink System Period control (see the topic Simulink System Period above) on the
System Generator block is hierarchical. A hierarchical control on a System Generator block
applies to the portion of the design within the scope of the block, but can be overridden on
other System Generator blocks deeper in the design. For example, suppose Simulink
System Period is set in a System Generator block at the top of the design, but is changed in
a System Generator block within a subsystem S. Then that subsystem will have the second
period, but the rest of the design will use the period set in the top level.
Compilation Results
In topic discusses the low-level files System Generator produces when HDL Netlist is
selected on the System Generator block and Generate is clicked. The files consist of HDL,
NGC and EDIF that implement the design. In addition, System Generator produces
auxiliary files that simplify downstream processing, e.g., bringing the design into Project
Navigator, simulating using an HDL simulator, and synthesizing using various synthesis
tools. All files are written to the target directory specified on the System Generator block. If
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no testbench is requested, then the key files produced by System Generator are the
following:
File Name or Type
Description
<design>.vhd/.v
This contains most of the HDL for the design
<design>_cw.vhd/.v
This is a HDL wrapper for <design>_files.vhd/.v. It
drives clocks and clock enables.
.edn and .ngc files
Besides writing HDL, System Generator runs CORE Generator
(coregen) to implement portions of the design. Coregen writes
EDIF files whose names typically look something like
multiplier_virtex2_6_0_83438798287b830b.edn.
Other required files may be supplied as .ngc files.
globals
This file consists of key/value pairs that describe the design.
The file is organized as a Perl hash table so that the keys and
values can be made available to Pearl scripts using Perl evals.
<design>_cw.xcf (or .ncf)
This contains timing and port location constraints. These are
used by the Xilinx synthesis tool XST and the Xilinx
implementation tools. If the synthesis tool is set to something
other than XST, then the suffix is changed to .ncf.
<design>_cw.ise
This allows the HDL and EDIF to be brought into the Xilinx
project management tool Project Navigator.
hdlFiles
This contains the full list of HDL files written by System
Generator. The files are listed in the usual HDL dependency
order.
synplify_<design>.prj, or
These files allow the design to be compiled by the synthesis
tool you specified.
xst_<design>.pr
vcom.do
This script can be used in ModelSim to compile the HDL for a
behavioral simulation of the design.
If a testbench is requested, then, in addition to the above, System Generator produces files
that allow simulation results to be compared. The comparisons are between Simulink
simulation results and corresponding results from ModelSim. The additional files are the
following:
File Name or Type
Description
Various .dat files
These contain the simulation results from Simulink.
<design>_tb.vhd/.v
This is a testbench that wraps the design. When simulated in
ModelSim, this testbench compares simulation results from
Simulink against those produced by ModelSim.
vsim.do
This script can be used in ModelSim to run a testbench
simulation.
pn_behavioral.do,
pn_postmap.do,
pn_postpar.do,
pn_posttranslate.do
These files allow various ModelSim simulations to be started
inside Project Navigator.
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Using the System Generator Constraints File
When a design is compiled, System Generator produces a constraints file that tells
downstream tools how to process the design. This enables the tools to produce a higher
quality implementation, and to do so using considerably less time. Constraints supply the
following:
•
The period to be used for the system clock;
•
The speed, with respect to the system clock, at which various portions of the design
must run;
•
The pin locations at which ports should be placed;
•
The speed at which ports must operate.
The file format depends on the synthesis tool that is specified in the System Generator
block. When XST is selected, the file is written in the XCF format; for Synplify and Synplify
Pro, the NCF format is used. The file name ends with.xcf or .ncf, as appropriate.
System Clock Period
The system clock period (i.e., the period of the fastest hardware clock in the design) can be
specified in the System Generator block. System Generator writes this period to the
constraints file. Downstream tools use the period as a goal when implementing the design.
Multicycle Path Constraints
Many designs consist of parts that run at different clock rates. For the fastest part, the
system clock period is used. For the remaining parts, the clock period is an integer multiple
of the system clock period. It is important that downstream tools know what speed each
part of the design must achieve. With this information, efficiency and effectiveness of the
tools are greatly increased, resulting in reduced compilation times and improved
hardware realizations. The division of the design into parts, and the speed at which each
part must run, are specified in the constraints file using multicycle path constraints.
IOB Timing and Placement Constraints
When translated into hardware, System Generator's Gateway In and Gateway Out blocks
become input and output ports. The locations of these ports and the speeds at which they
must operate can be entered in the Gateway In and Out parameter dialog boxes.
See the descriptions of the Gateway In block and the Gateway Out block for more
information. Port location and speed are specified in the constraints file by IOB timing.
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Constraints Example
The figure below shows a small multirate design and the constraints System Generator
produces for it.
The up sampler doubles the rate, and the down sampler divides the rate by three. Assume
the system clock period is 10 ns. Then the clock periods are 10 ns for the FIR, 20 ns for the
input register, and 30 ns for the output register. The following text describes the constraints
that convey this information.
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The lines that indicate the system clock period is10 ns are the following:
# Global period constraint
NET "clk" TNM_NET = "clk_392b7670";
TIMESPEC "TS_clk_392b7670" = PERIOD "clk_392b7670" 10.0 ns HIGH 50 %;
To build timing constraints, the blocks in the design are partitioned into timing groups.
Two blocks are in the same timing group if and only if they run at the same sample rate. In
this design there are three timing groups, corresponding to the three rates. The nature of
constraints dictates that no name is needed for the fastest group. The remaining groups are
named ce_2_392b7670_group and ce_3_392b7670_group; they correspond to periods 20 ns
and 30 ns respectively.
The FIR runs at the system (i.e., fastest) rate and therefore is constrained using the global
period constraint shown above. The logic used to generate clocks always runs at the
system rate and is also constrained to the system rate.
The ce_2_392b7670_group consists of the blocks that operate at half the system rate, i.e., the
input register and the up sampler. Every block in the group is driven by the clock enable
net named ce2_sysgen. The constraints that define the group are the following:
# ce_2_392b7670_group and inner group constraint
Net "ce_2_sg_x0*" TNM_NET = "ce_2_392b7670_group";
TIMESPEC "TS_ce_2_392b7670_group_to_ce_2_392b7670_group" = FROM
"ce_2_392b7670_group" TO "ce_2_392b7670_group" 20.0 ns;
Note: A wildcard character is added to the net name to constrain any additional copies of this net
that may be generated when clock enable logic is replicated. The maximum fanout of a clock enable
net can be controlled in the synthesis tool.
The ce_3_392b7670_group operates at one third the system rate. It contains the down
sampler and the output register, and is defined in a similar manner to the ce2_group.
# ce_3_392b7670_group and inner group constraint
Net "ce_3_sg_x0*" TNM_NET = "ce_3_392b7670_group";
TIMESPEC "TS_ce_3_392b7670_group_to_ce_3_392b7670_group" = FROM
"ce_3_392b7670_group" TO "ce_3_392b7670_group" 30.0 ns;
Group to group constraints establish relative speeds. Here are the constraints that relate
the speeds of ce_2_392b7670_group and ce_3_392b7670_group:
# Group-to-group constraints
TIMESPEC "TS_ce_2_392b7670_group_to_ce_3_392b7670_group" = FROM
"ce_2_392b7670_group" TO "ce_3_392b7670_group" 20.0 ns;
TIMESPEC "TS_ce_3_392b7670_group_to_ce_2_392b7670_group" = FROM
"ce_3_392b7670_group" TO "ce_2_392b7670_group" 20.0 ns;
Port timing requirements can be set in the parameter dialog boxes for gateways. These
requirements are translated into port constraints such as those shown below. In this
example, the 3-bit din input is constrained to operate at its gateway's sample rate
(corresponding to a period of 20 ns). The "FAST" attributes indicate the ports should be
implemented using hardware that reduces delay. The reduction comes at a cost of
increased noise and power consumption.
# Offset in constraints
NET "din(0)" OFFSET = IN : 20.0 : BEFORE "clk";
NET "din(0)" FAST;
NET "din(1)" OFFSET = IN : 20.0 : BEFORE "clk";
NET "din(1)" FAST;
NET "din(2)" OFFSET = IN : 20.0 : BEFORE "clk";
NET "din(2)" FAST;
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Selecting Specify IOB Location Constraints for a gateway allows port locations to be
specified. The locations must be entered as a cell array of strings in the box labeled IOB
Pad Locations. Locations are package-specific; in this example a Virtex-E 2000 in a FG680
package is used. The location constraints for the din bus are provided in the dialog box as
"{'D35', 'B36', 'C35' }". This is translated into constraints in the .xcf (or .ncf) file in the
following way:
# Loc constraints
NET "din(2)" LOC = "D35";
NET "din(1)" LOC = "B36";
NET "din(0)" LOC = "C35";
Clock Handling in HDL
Clock Handling in HDL
This topic describes how System Generator handles hardware clocks in the HDL it
generates. Assume the design is named <design>, and <design> is an acceptable HDL
identifier. When System Generator compiles the design, it writes a collection of HDL
entities or modules, the topmost of which is named <design>, and is stored in a file
named <design>.vhd/.v.
Clock and clock enables appear in pairs throughout the HDL. Typical clock names are
clk_1, clk_2, and clk_3, and the names of the companion clock enables are ce_1, ce_2, and
ce_3 respectively. The name tells the rate for the clock/clock enable pair; logic driven by
clk_1 and ce_1 runs at the system (i.e., fastest) rate, while logic driven by (say) clk_2 and
ce_2 runs at half the system rate. Clocks and clock enables are not driven in the entity or
module named <design> or any subsidiary entities; instead, they are exposed as top-level
input ports
Of course, there must be a way to generate these clocks and clock enables. System
Generator produces a separate clock wrapper (written to a file named
<design>_cw.vhd/.v) to do this. This wrapper is external to the files described above.
The idea is to make the HDL flexible. In some applications, the files described above are
added to a larger design, but the clock wrapper is omitted. In this case, you are responsible
for generating clocks and clock enables, but a finer degree of control is obtained. If, on the
other hand, the clock wrapper is suitable for the application, then include it. As an
additional convenience, System Generator generates a DCM wrapper (written to a file
named <design>_dw_vhd/_v) that encloses the clock wrapper. The DCM wrapper
deskews the hardware FPGA clock. When incorporating System Generator HDL into a
larger design, each of the following is possible:
•
Use the HDL that System Generator writes, but exclude the clock and DCM wrappers;
•
Use the HDL that System Generator writes, and use the clock wrapper, but exclude
the DCM wrapper.
•
Use the HDL that System Generator writes, and use both the clock and DCM
wrappers.
If you want to use the DCM wrapper in your work, rename the file by replacing the final
_vhd or _v with .vhd or .v.
The names of the clocks and clock enables in System Generator HDL suggest that clocking
is completely general, but this is not the case. To illustrate this, assume a design has clocks
named clk_1 and clk_2, and companion clock enables named ce_1 and ce_2 respectively.
The reader might expect that working hardware could be produced if the ce_1 and ce_2
signals were tied high, and clk_2 were driven by a clock signal whose rate is half that of
clk_1. For most System Generator designs this does not work. Instead, clk_1 and clk_2 must
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be driven by the same clock, ce_1 must be tied high, and ce_2 must vary at a rate half that
of clk_1 and clk_2.
The clock wrapper consists of two components: one for the design itself, and one clock
driver component that generate clocks and clock enables. The clock driver is contained in a
file named <design>_cw.vhd/.v. The logic within the <design>_cw generates the
ce_x signals. The optional ce_clr port would be generated if the design was generated
by selecting Provide clock enable clear pin on the System Generator block. The ports that
are not clocks or clock enables are passed through to the exterior of the clock wrapper.
Schematically, the clock wrapper looks like the diagram below.
Note: The clock wrapper exposes a port named ce. The port does nothing except to serve as a
companion to the clk port on the wrapper. The reason for having the port is to allow the clock wrapper
to be used as a black box in System Generator designs.
Core Caching
System Generator uses cores produced by Xilinx CORE Generator (coregen) to implement
parts of designs. Generating cores can be expensive, so System Generator caches
previously generated ones. Before coregen is called, System Generator looks in the cache,
and if the core has already been generated, System Generator reuses it.
By default, the cache is the directory $TEMP/sg_core_cache. And by default, System
Generator caches no more than 2,000 cores. When the limit is reached, System Generator
deletes cached cores to make room for new ones.
Note: Environment variables can be used to change the location of the cache and the cache size
limit. The variables are described below.
Environment Variable
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Description
SGCORECACHE
Location to store cached files. Setting this variable to a string of
blanks instructs System Generator not to cache cores.
SGCORECACHELIMIT
Maximum number of cores to cache.
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HDL Testbench
Ordinarily, System Generator designs are bit and cycle-accurate, so Simulink simulation
results exactly match those seen in hardware. There are, however, times when it is useful to
compare Simulink simulation results against those obtained from an HDL simulator. In
particular, this makes sense when the design contains black boxes. The Create Testbench
checkbox in the System Generator block makes this possible.
Suppose the design is named <design>, and a System Generator block is placed at the top
of the design. Suppose also that in the block the Compilation field is set to HDL Netlist,
and the Create Testbench checkbox is selected. When the Generate button is clicked,
System Generator produces the usual files for the design, and in addition writes the
following:
1.
A file named <design>_tb.vhd/.v that contains a testbench HDL entity;
2.
Various .dat files that contain test vectors for use in an HDL testbench simulation.
3.
Scripts vcom.do and vsim.do that can be used in ModelSim to compile and simulate
the testbench, comparing Simulink test vectors against those produced in HDL.
System Generator generates the .dat files by saving the values that pass through
gateways. In the HDL simulation, input values from the .dat files are stimuli, and output
values are expected results. The testbench is simply a wrapper that feeds the stimuli to the
HDL for the design, then compares HDL results against expected ones.
Compiling MATLAB into an FPGA
System Generator provides direct support for MATLAB through the MCode block. The
MCode block applies input values to an M-function for evaluation using Xilinx's fixedpoint data type. The evaluation is done once for each sample period. The block is capable
of keeping internal states with the use of persistent state variables. The input ports of the
block are determined by the input arguments of the specified M-function and the output
ports of the block are determined by the output arguments of the M-function. The block
provides a convenient way to build finite state machines, control logic, and computation
heavy systems.
In order to construct an MCode block, an M-function must be written. The M-file must be
in the directory of the model file that is to use the M-file or in a directory in the MATLAB
path.
This tutorial provides ten examples that use the MCode block:
•
Example 1 Simple Selector shows how to implement a function that returns the
maximum value of its inputs;
•
Example 2 Simple Arithmetic Operations shows how to implement simple arithmetic
operations;
•
Example 3 Complex Multiplier with Latency shows how to build a complex
multiplier with latency;
•
Example 4 Shift Operations shows how to implement shift operations;
•
Example 5 Passing Parameters into the MCode Block shows how to pass parameters
into a MCode block;
•
Example 6 Optional Input Ports shows how to implement optional input ports on an
MCode block;
•
Example 7 Finite State Machines shows how to implement a finite state machine;
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Example 8 Parameterizable Accumulator shows how to build a parameterizable
accumulator;
•
Example 9 FIR Example and System Verification shows how to model FIR blocks and
how to do system verification;
•
Example 10 RPN Calculator shows how to model a RPN calculator – a stack machine;
•
Example 11 Example of disp Function shows how to use disp function to print
variable values.
The first two examples are in the mcode_block_tutorial.mdl file of the
examples/mcode_block directory in your installation of the System Generator software.
Examples 3 and 4 are in the mcode_block_tutorial2.mdl file. Examples 5 and 6 are in the
mcode_block_tutorial3.mdl file. Examples 7 and 8 are in the mcode_block_tutorial4.mdl
file. Example 9 is mcode_block_verify_fir.mdl. Example 10 is in
mcode_block_rpn_calculator.mdl.
Simple Selector
This example is a simple controller for a data path, which assigns the maximum value of
two inputs to the output. The M-function is specified as the following and is saved in an Mfile xlmax.m:
function z = xlmax(x, y)
if x > y
z = x;
else
z = y;
end
The xlmax.m file should be either saved in the same directory of the model file or should
be in the MATLAB path. Once the xlmax.m has been saved to the appropriate place, you
should drag a MCode block into your model, open the block parameter dialog box, and
enter xlmax into the MATLAB Function field. After clicking the OK button, the block has
two input ports x and y, and one output port z.
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The following figure shows what the block looks like after the model is compiled. You can
see that the block calculates and sets the necessary fixed-point data type to the output port.
Simple Arithmetic Operations
This example shows some simple arithmetic operations and type conversions. The
following shows the xlSimpleArith.m file, which specifies the xlSimpleArith Mfunction.
function [z1, z2, z3, z4] = xlSimpleArith(a, b)
% xlSimpleArith demonstrates some of the arithmetic operations
% supported by the Xilinx MCode block. The function uses xfix()
% to create Xilinx fixed-point numbers with appropriate
% container types.%
% You must use a xfix() to specify type, number of bits, and
% binary point position to convert floating point values to
% Xilinx fixed-point constants or variables.
% By default, the xfix call uses xlTruncate
% and xlWrap for quantization and overflow modes.
% const1 is Ufix_8_3
const1 = xfix({xlUnsigned, 8, 3}, 1.53);
% const2 is Fix_10_4
const2 = xfix({xlSigned, 10, 4, xlRound, xlWrap}, 5.687);
z1 = a + const1;
z2 = -b - const2;
z3 = z1 - z2;
% convert z3 to Fix_12_8 with saturation for overflow
z3 = xfix({xlSigned, 12, 8, xlTruncate, xlSaturate}, z3);
% z4 is true if both inputs are positive
z4 = a>const1 & b>-1;
This M-function uses addition and subtraction operators. The MCode block calculates
these operations in full precision, which means the output precision is sufficient to carry
out the operation without losing information.
One thing worth discussing is the xfix function call. The function requires two
arguments: the first for fixed-point data type precision and the second indicating the value.
The precision is specified in a cell array. The first element of the precision cell array is the
type value. It can be one of three different types: xlUnsigned, xlSigned, or xlBoolean.
The second element is the number of bits of the fixed-point number. The third is the binary
point position. If the element is xlBoolean, there is no need to specify the number of bits
and binary point position. The number of bits and binary point position must be specified
in pair. The fourth element is the quantization mode and the fifth element is the overflow
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mode. The quantization mode can be one of xlTruncate, xlRound, or xlRoundBanker.
The overflow mode can be one of xlWrap, xlSaturate, or xlThrowOverflow.
Quanitization mode and overflow mode must be specified as a pair. If the quantizationoverflow mode pair is not specified, the xfix function uses xlTruncate and xlWrap for
signed and unsigned numbers. The second argument of the xfix function can be either a
double or a Xilinx fixed-point number. If a constant is an integer number, there is no need
to use the xfix function. The Mcode block converts it to the appropriate fixed-point
number automatically.
After setting the dialog box parameter MATLAB Function to xlSimpleArith, the block
shows two input ports a and b, and four output ports z1, z2, z3, and z4.
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M-functions using Xilinx data types and functions can be tested in the MATLAB command
window. For example, if you type: [z1, z2, z3, z4] = xlSimpleArith(2, 3) in
the MATLAB command window, you'll get the following lines:
UFix(9, 3): 3.500000
Fix(12, 4): -8.687500
Fix(12, 8): 7.996094
Bool: true
Notice that the two integer arguments (2 and 3) are converted to fixed-point numbers
automatically. If you have a floating-point number as an argument, an xfix call is
required.
Complex Multiplier with Latency
This example shows how to create a complex number multiplier. The following shows the
xlcpxmult.m file which specifies the xlcpxmult function.
function [xr, xi] = xlcpxmult(ar, ai, br, bi)
xr = ar * br - ai * bi;
xi = ar * bi + ai * br;
The following diagram shows the sub-system:
Two delay blocks are added after the MCode block. By selecting the option Implement
using behavioral HDL on the Delay blocks, the downstream logic synthesis tool is able to
perform the appropriate optimizations to achieve higher performance.
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Shift Operations
This example shows how to implement bit-shift operations using the MCode block. Shift
operations are accomplished with multiplication and division by powers of two. For
example, multiplying by 4 is equivalent to a 2-bit left-shift, and dividing by 8 is equivalent
to a 3-bit right-shift. Shift operations are implemented by moving the binary point position
and if necessary, expanding the bit width. Consequently, multiplying a Fix_8_4 number by
4 results in a Fix_8_2 number, and multiplying a Fix_8_4 number by 64 results in a
Fix_10_0 number.
The following shows the xlsimpleshift.m file which specifies one left-shift and one
right-shift:
function [lsh3, rsh2] = xlsimpleshift(din)
% [lsh3, rsh2] = xlsimpleshift(din) does a left shift
% 3 bits and a right shift 2 bits.
% The shift operation is accomplished by
% multiplication and division of power
% of two constant.
lsh3 = din * 8;
rsh2 = din / 4;
The following diagram shows the sub-system after compilation:
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Passing Parameters into the MCode Block
This example shows how to pass parameters into the MCode block. An input argument to
an M-function can be interpreted either as an input port on the MCode block, or as a
parameter internal to the block.
The following M-code defines an M-function xl_sconvert is contained in file
xl_sconvert.m:
function dout = xl_sconvert(din, nbits, binpt)
proto = {xlSigned, nbits, binpt};
dout = xfix(proto, din);
The following diagram shows a subsystem containing two MCode blocks that use Mfunction xl_sconvert. The arguments nbits and binpt of the M-function are specified
differently for each block by passing different parameters to the MCode blocks. The
parameters passed to the MCode block labeled signed convert 1 cause it to convert
the input data from type Fix_16_8 to Fix_10_5 at its output. The parameters passed to
the MCode block labeled signed convert2 causes it to convert the input data from type
Fix_16_8 to Fix_8_4 at its output.
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To pass parameters to each MCode block in the diagram above, you can click the Edit
Interface button on the block GUI then set the values for the M-function arguments. The
mask for MCode block signed convert 1 is shown below:
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The above interface window sets the M-function argument nbits to be 10 and binpt to
be 5. The mask for the MCode block signed convert 2 is shown below:
The above interface window sets the M-function argument nbits to be 8 and binpt to be
4.
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Optional Input Ports
This example shows how to use the parameter passing mechanism of MCode blocks to
specify whether or not to use optional input ports on MCode blocks.
The following M-code, which defines M-function xl_m_addsub is contained in file
xl_m_addsub.m:
function s = xl_m_addsub(a, b, sub)
if sub
s = a - b;
else
s = a + b;
end
The following diagram shows a subsystem containing two MCode blocks that use Mfunction xl_m_addsub.
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The Block Interface Editor of the MCode block labeled add is shown in below.
As a result, the add block features two input ports a and b; it performs full precision
addition. Input parameter sub of the MCode block labeled addsub is not bound with any
value. Consequently, the addsub block features three input ports: a, b, and sub; it
performs full precision addition or subtraction based on the value of input port sub.
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Finite State Machines
This example shows how to create a finite state machine using the MCode block with
internal state variables. The state machine illustrated below detects the pattern 1011 in an
input stream of bits.
The M-function that is used by the MCode block contains a transition function, which
computes the next state based on the current state and the current input. Unlike example 3
though, the M-function in this example defines persistent state variables to store the state
of the finite state machine in the MCode block. The following M-code, which defines
function detect1011_w_state is contained in file detect1011_w_state.m:
function matched = detect1011_w_state(din)
% This is the detect1011 function with states for detecting a
% pattern of 1011.
seen_none = 0; %
seen_1 = 1;
%
%
seen_10 = 2;
%
%
seen_101 = 3; %
%
initial state, if input is 1, switch to seen_1
first 1 has been seen, if input is 0, switch
seen_10
10 has been detected, if input is 1, switch to
seen_1011
now 101 is detected, is input is 1, 1011 is
detected and the FSM switches to seen_1
% the state is a 2-bit register
persistent state, state = xl_state(seen_none, {xlUnsigned, 2, 0});
% the default value of matched is false
matched = false;
switch state
case seen_none
if din==1
state = seen_1;
else
state = seen_none;
end
case seen_1 % seen first 1
if din==1
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state = seen_1;
else
state = seen_10;
end
case seen_10 % seen 10
if din==1
state = seen_101;
else
% no part of sequence seen, go to seen_none
state = seen_none;
end
case seen_101
if din==1
state = seen_1;
matched = true;
else
state = seen_10;
matched = false;
end
end
The following diagram shows a state machine subsystem containing a MCode block after
compilation; the MCode block uses M-function detect1101_w_state.
Parameterizable Accumulator
This example shows how to use the MCode block to build an accumulator using persistent
state variables and parameters to provide implementation flexibility. The following Mcode, which defines function xl_accum is contained in file xl_accum.m:
function q = xl_accum(b, rst, load, en, nbits, ov, op,
feed_back_down_scale)
% q = xl_accum(b, rst, nbits, ov, op, feed_back_down_scale) is
% equivalent to our Accumulator block.
binpt = xl_binpt(b);
init = 0;
precision = {xlSigned, nbits, binpt, xlTruncate, ov};
persistent s, s = xl_state(init, precision);
q = s;
if rst
if load
% reset from the input port
s = b;
else
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% reset from zero
s = init;
end
else
if ~en
else
% if enabled, update the state
if op==0
s = s/feed_back_down_scale + b;
else
s = s/feed_back_down_scale - b;
end
end
end
The following diagram shows a subsystem containing the accumulator MCode block using
M-function xl_accum. The MCode block is labeled MCode Accumulator. The
subsystem also contains the Xilinx Accumulator block, labeled Accumulator, for
comparison purposes. The MCode block provides the same functionality as the Xilinx
Accumulator block; however, its mask interface differs in that parameters of the MCode
block are specified with a cell array in the Function Parameter Bindings parameter.
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Optional inputs rst and load of block Accum_MCode1 are disabled in the cell array of the
Function Parameter Bindings parameter. The block mask for block MCode Accumulator is
shown below:
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The example contains two additional accumulator subsystems with MCode blocks using
the same M-function, but different parameter settings to accomplish different accumulator
implementations.
FIR Example and System Verification
This example shows how to use the MCode block to model FIRs. It also shows how to do
system verification with the MCode block.
The model contains two FIR blocks. Both are modeled with the MCode block and both are
synthesizable. The following are the two functions that model those two blocks.
function y = simple_fir(x, lat, coefs, len, c_nbits, c_binpt, o_nbits,
o_binpt)
coef_prec = {xlSigned, c_nbits, c_binpt, xlRound, xlWrap};
out_prec = {xlSigned, o_nbits, o_binpt};
coefs_xfix
persistent
persistent
persistent
= xfix(coef_prec, coefs);
coef_vec, coef_vec = xl_state(coefs_xfix, coef_prec);
x_line, x_line = xl_state(zeros(1, len-1), x);
p, p = xl_state(zeros(1, lat), out_prec, lat);
sum = x * coef_vec(0);
for idx = 1:len-1
sum = sum + x_line(idx-1) * coef_vec(idx);
sum = xfix(out_prec, sum);
end
y = p.back;
p.push_front_pop_back(sum);
x_line.push_front_pop_back(x);
function y = fir_transpose(x, lat, coefs, len, c_nbits, c_binpt,
o_nbits, o_binpt)
coef_prec = {xlSigned, c_nbits, c_binpt, xlRound, xlWrap};
out_prec = {xlSigned, o_nbits, o_binpt};
coefs_xfix = xfix(coef_prec, coefs);
persistent coef_vec, coef_vec = xl_state(coefs_xfix, coef_prec);
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persistent reg_line, reg_line = xl_state(zeros(1, len), out_prec);
if lat <= 0
error('latency must be at least 1');
end
lat = lat - 1;
persistent dly,
if lat <= 0
y = reg_line.back;
else
dly = xl_state(zeros(1, lat), out_prec, lat);
y = dly.back;
dly.push_front_pop_back(reg_line.back);
end
for idx = len-1:-1:1
reg_line(idx) = reg_line(idx - 1) + coef_vec(len - idx - 1) * x;
end
reg_line(0) = coef_vec(len - 1) * x;
The parameters are configured as following:
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In order to verify that the functionality of two blocks are equal, we also use another MCode
block to compare the outputs of two blocks. If the two outputs are not equal at any given
time, the error checking block will report the error. The following function does the error
checking:
function eq = error_ne(a, b, report, mod)
persistent cnt, cnt = xl_state(0, {xlUnsigned, 16, 0});
switch mod
case 1
eq = a==b;
case 2
eq = isnan(a) || isnan(b) || a == b;
case 3
eq = ~isnan(a) && ~isnan(b) && a == b;
otherwise
eq = false;
error(['wrong value of mode ', num2str(mod)]);
end
if report
if ~eq
error(['two inputs are not equal at time ', num2str(cnt)]);
end
end
cnt = cnt + 1;
The block is configured as following:
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RPN Calculator
This example shows how to use the MCode block to model a RPN calculator which is a
stack machine. The block is synthesizable.
The following function models the RPN calculator.
function [q, active] = rpn_calc(d, rst, en)
d_nbits = xl_nbits(d);
% the first bit indicates whether it's a data or operator
is_oper = xl_slice(d, d_nbits-1, d_nbits-1)==1;
din = xl_force(xl_slice(d, d_nbits-2, 0), xlSigned, 0);
% the lower 3 bits are operator
op = xl_slice(d, 2, 0);
% acc the the A register
persistent acc, acc = xl_state(0, din);
% the stack is implemented with a RAM and
% an up-down counter
persistent mem, mem = xl_state(zeros(1, 64), din);
persistent acc_active, acc_active = xl_state(false, {xlBoolean});
persistent stack_active, stack_active = xl_state(false, ...
{xlBoolean});
stack_pt_prec = {xlUnsigned, 5, 0};
persistent stack_pt, stack_pt = xl_state(0, {xlUnsigned, 5, 0});
% when en is true, it's action
OP_ADD = 2;
OP_SUB = 3;
OP_MULT = 4;
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OP_NEG = 5;
OP_DROP = 6;
q = acc;
active = acc_active;
if rst
acc = 0;
acc_active = false;
stack_pt = 0;
elseif en
if ~is_oper
% enter data, push
if acc_active
stack_pt = xfix(stack_pt_prec, stack_pt + 1);
mem(stack_pt) = acc;
stack_active = true;
else
acc_active = true;
end
acc = din;
else
if op == OP_NEG
% unary op, no stack op
acc = -acc;
elseif stack_active
b = mem(stack_pt);
switch double(op)
case OP_ADD
acc = acc + b;
case OP_SUB
acc = b - acc ;
case OP_MULT
acc = acc * b;
case OP_DROP
acc = b;
end
stack_pt = stack_pt - 1;
elseif acc_active
acc_active = false;
acc = 0;
end
end
end
stack_active = stack_pt ~= 0;
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Example of disp Function
The following MCode function shows how to use the disp function to print variable
values.
function x = testdisp(a, b)
persistent dly, dly = xl_state(zeros(1, 8), a);
persistent rom, rom = xl_state([3, 2, 1, 0], a);
disp('Hello World!');
disp(['num2str(dly) is ', num2str(dly)]);
disp('disp(dly) is ');
disp(dly);
disp('disp(rom) is ');
disp(rom);
a2 = dly.back;
dly.push_front_pop_back(a);
x = a + b;
disp(['a = ', num2str(a), ', ', ...
'b = ', num2str(b), ', ', ...
'x = ', num2str(x)]);
disp(num2str(true));
disp('disp(10) is');
disp(10);
disp('disp(-10) is');
disp(-10);
disp('disp(a) is ');
disp(a);
disp('disp(a == b)');
disp(a==b);
The Enable print with disp option must be checked.
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Here are the lines that are displayed on the MATLAB console for the first simulation step.
mcode_block_disp/MCode (Simulink time: 0.000000, FPGA clock: 0)
Hello World!
num2str(dly) is [0.000000, 0.000000, 0.000000, 0.000000, 0.000000,
0.000000, 0.000000, 0.000000]
disp(dly) is
type: Fix_11_7,
maxlen: 8,
length: 8,
0: binary 0000.0000000, double 0.000000,
1: binary 0000.0000000, double 0.000000,
2: binary 0000.0000000, double 0.000000,
3: binary 0000.0000000, double 0.000000,
4: binary 0000.0000000, double 0.000000,
5: binary 0000.0000000, double 0.000000,
6: binary 0000.0000000, double 0.000000,
7: binary 0000.0000000, double 0.000000,
disp(rom) is
type: Fix_11_7,
maxlen: 4,
length: 4,
0: binary 0011.0000000, double 3.0,
1: binary 0010.0000000, double 2.0,
2: binary 0001.0000000, double 1.0,
3: binary 0000.0000000, double 0.0,
a = 0.000000, b = 0.000000, x = 0.000000
1
disp(10) is
type: UFix_4_0, binary: 1010, double: 10.0
disp(-10) is
type: Fix_5_0, binary: 10110, double: -10.0
disp(a) is
type: Fix_11_7, binary: 0000.0000000, double: 0.000000
disp(a == b)
type: Bool, binary: 1, double: 1
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Importing a System Generator Design into a Bigger System
Importing a System Generator Design into a Bigger System
A System Generator design is often a sub-design that is incorporated into a larger HDL
design. This topic shows how to embed two System Generator designs into a larger design
and how VHDL created by System Generator can be incorporated into the simulation
model of the overall system.
Starting with Release 10.1, System Generator introduces a new integration flow between
System Generator (Sysgen) and Project Navigator (ProjNav). This first phase of integration
concentrates on the following areas:
•
Allows you to add a System Generator design as a sub-level to a larger design
•
Consolidates and associates System Generator constraints to the top-level design
•
Enables you to perform certain design iterations between Project Navigator and the
System Generator design
HDL Netlist Compilation
Selecting the HDL Netlist compilation target from the System Generator token instructs
System Generator to generate HDL along with other related files such as NGC files and
EDIF files that implement the design. In addition, System Generator produces auxiliary
files that simplify downstream processing such as bringing the design into Project
Navigator, simulating the design using an HDL simulator, and performing logic synthesis
using various logic synthesis tools. See the topic System Generator Compilation Types for
more details.
Starting with Release 10.1, the System Generator project information is encapsulated in the
file <design_name>_cw.sgp or <design_name>_mcw.sgp depending on which
clocking option is selected. This topic shows how multiple System Generator designs can
be included as sub-modules in a larger design.
Integration Design Rules
When a System Generator model is to be included into a larger design, the following two
design rules must be followed.
Rule 1: No Gateway or System Generator token should specify an IOB/CLK location
constraint. Otherwise, the NGDBuild tool will issue the following warning:
WARNING:NgdBuild:483 - Attribute "LOC" on "clk" is on the wrong type
of object. Please see the Constraints Guide for more information on
this attribute.
Rule 2: If there are any I/O ports from the System Generator design that are required to be
bubbled up to the top-level design, appropriate buffers should be instantiated in the toplevel HDL code.
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New Integration Flow between System Generator & Project Navigator
The illustration below shows the entire flow of how multiple System Generator designs
can be integrated into Project Navigator as lower-level designs. System Generator
generates a project file with an extension .sgp that you can add as a System Generator
source type in Project Navigator. This file contains all necessary information about the
System Generator design, including file locations and constraint files. Prior to the
integration with Project Navigator in Release 10.1, you had to manually consolidate and
associate UCF constraints into the top-level design. It is now done automatically during
the implementation in Project Navigator as shown in the following figure.
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A Step-by-Step Example
In this example, two HDL netlists from System Generator are integrated into a larger
VHDL design. Design #1 is named SPRAM and design #2 is named MAC_FIR. The toplevel VHDL entity combines the two data ports and a control signal from the SPRAM
design to create a bidirectional bus. The top-level VHDL also instantiates the MAC_FIR
design and supplies a separate clock signal named clk2. A block diagram of this design is
shown below.
The files used in this example are located in the System Generator tree at pathname
<sysgen_tree>/examples/projnav/mult_diff_designs. The following files are
provided:
•
spram.mdl - System Generator design #1
•
mac_fir.mdl - System Generator design #2
Files within the sub-directory named top_level:
•
top_level.ise – ProjNav project for compiling top_level design
•
top_level.vhd – Top-level VHDL file
•
top_level_testbench.do – Custom ModelSim .do file
•
top_level_testbench.vhd – Top-level VHDL testbench file
•
wave.do – ModelSim .do file called by top_level_testbench.do to display
waveforms
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Generating the HDL Files for the System Generator Designs
The steps used to create the HDL files are as follows:
1.
Open the first design, spram.mdl, in MATLAB. This is a multirate design due to the
down sampling block placed after the output of the Single Port RAM. You should
verify that the constraints for this design have been applied properly by looking at the
PAR report.
2.
Double click on the System Generator block; select the HDL Netlist target and press
the Generate button. By pressing the Generate button, the HDL file for this design is
created in the directory
<sysgen_tree>/examples/projnav/mult_diff_designs/hdl_netlist1.
3.
Repeat steps 1 and 2 for the mac_fir.mdl model. The HDL file for this design is
created in the directory
<sysgen_tree>/examples/projnav/mult_diff_designs/hdl_netlist2.
Note: You are now finished generating HDL Netlists from System Generator
Switching to Different HDL Libraries
When integrating two or more System Generator designs into a bigger design, you need to
rename HDL libraries to prevent name clashes and other undesired behaviors during
simulation. System Generator provides a utility that switches library names for all related
files in your System Generator design. In addition, it also makes a backup copy in a folder
just in case you want to revert back to the original library name. The following is the syntax
for this utility:
Syntax:
xlSwitchLibrary(<target_dir_pathname>, <from_lib_name>, <to_lib_name>)
<target_dir_pathname>: location of the design
<from_lib_name>: Original HDL library name
<to_lib_name>: New HDL library name
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1.
From the MATLAB Console, enter the following command:
xlSwitchLibrary('hdl_netlist1','work','design1_lib')
2.
Next, from the MATLAB Console, enter the following command:
xlSwitchLibrary('hdl_netlist2','work','design2_lib')
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The transcript should look similar to the following:
Adding System Generator Source into the Top-Level Design
The next two steps are used to synthesize the top_level design:
1.
Launch ISE and reload the pre-generated top-level design ISE project at
~top_level/top_level.ise.
Note: At this point, your Project Navigator should look like the figure below. Both spram_cw and
mac_fir_cw instances are instantiated at the top_level design. But since they are not located on the
same directory as the top-level design, Project Navigator puts a question mark next to each one of
them to indicate that it can not find these two instances / modules.
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:
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2.
Add the System Generator source: under the Sources tab, right-click on
u_spram_cw -> Add Source…at
<sysgen_tree>/examples/projnav/mult_diff_designs/hdl_netlist1/s
pram_cw.sgp
3.
Repeat item 2 with u_mac_fir at
<sysgen_tree>/examples/projnav/mult_diff_designs/hdl_netlist2/m
ac_fir_cw.sgp
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Importing a System Generator Design into a Bigger System
4.
As shown below, make sure the file top_level is selected, then implement the design
by double clicking on Processes tab > Implement Design. Once the implementation is
finished, Project Navigator should look like the figure below.
5.
Examine the timing constraints in the PAR report file: Processes tab > Implement
Design > Place & Route > Place & Route Report
Note that in the PAR report the multirate constraints were met:
1
2
3
4
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Constraints for each System Generator design were created and translated to a UCF (User
Constraint File). These UCF constraint files were then consolidated and associated during
ISE implementation (NGDBUILD). They are briefly described as follows:
A system sample period of 100 ns was set in the System Generator block for both designs
(1 & 2)
•
TS_clk_f488215c2 constraints are from the SRAM design (1)
•
The TS_clk_c4b7e2441 constraints are from the FIR design (2)
•
The ce16_c4b7e244_group_to_ce16_cb47e244_group1 constraint is for all the
synchronous elements after the down sampler and it is set to sixteen, the system
sample period (3)
•
The down sampling block in the SRAM design performs a down sample by 2. The
ce2_f488215c_group_to_ce2_f488215c_group2 constraint is for all the synchronous
elements after the down sampler and is set to twice the system sample period (4)
With the new integration between System Generator and Project Navigator, these
constraints are automatically associated and consolidated by Project Navigator up to the
top-level design. This flow is only available starting with Release 10.1.
Simulating the Entire Design
To perform a behavioral simulation of the top_level design, do the following:
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1.
System Generator creates VHDL files and invokes the selected logic synthesis tool to
generate the HDL Netlist. These VHDL files are used when simulating the top-level
design. The VHDL files generated for a design are named <design>_cw.vhd, and
<design>.vhd. Open the custom ModelSim do file named “top_level_testbench.do” to
see how the VHDL files for both designs are referenced.
2.
Memory initialization (.mif) and coefficient (.coe) files that are used during simulation
and must be placed in the same directory as the top-level VHDL file -- copy the .mif
and .coe files for both designs into the top_level directory.
3.
In ProjNav > Sources > change from Implementation to Behavioral Simulation
option from the pull-down menu. Select the top_level_testbenchstructural(top_level.vhd) source file. This file is imported into the project as a
testbench file, thus allowing you to simulate the design using the Simulator.
4.
In the Processes window, right click on Simulate Behavioral Model > Properties…
You should see a Simulation Properties dialog box as shown below. Note that A
Custom Do File has been specified as shown below (1).
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The previous screen shot shows the ModelSim commands used to compile the VHDL code
generated by System Generator. To simulate the top_level design, double left click on the
Simulate Behavioral Model process. The ModelSim .do file compiles the VHDL code and
runs the simulation for 10000 ns. The resulting waveform is shown below.
Summary
This topic has shown you how to import a System Generator Design into a larger system.
There are a few important things to keep in mind during each phase of the process.
While creating a System Generator design:
•
IOB constraints should not be specified on Gateways in the System Generator model;
neither should the System Generator block specify a clock pin location.
•
Use the HDL Netlist compilation target in the System Generator block. The HDL
Netlist file that System Generator produces contains both the RTL, EDIF and
constraint information for your design.
To instantiate the System Generator design in the top_level HDL:
•
Use a black box and assign the appropriate black box attribute The ce port is not
connected to registers within your design. It is provide so that the VHDL file can be
imported as a Black Box within System Generator.
For top-level simulation:
•
Create a custom ModelSim .do file in order to compile the VHDL files created by
System Generator. Modify the Project Navigator settings to use this custom .do file
New capabilities:
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•
Add System Generator Source type project file (.sgp) into Project Navigator as a submodule design
•
Consolidate and associate System Generator constraints into the top-level design
•
Launch MATLAB and System Generator MDL directly from Project Navigator to
perform certain design iterations
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Configurable Subsystems and System Generator
Configurable Subsystems and System Generator
A configurable subsystem is a kind of block that is made available as a standard part of
Simulink. In effect, a configurable subsystem is a block for which you can specify several
underlying blocks. Each underlying block is a possible implementation, and you are free to
choose which implementation to use. In System Generator you might, for example, specify
a general-purpose FIR filter as a configurable subsystem whose underlying blocks are
specific FIR filters. Some of the underlying filters might be fast but require much hardware,
while others are slow but require less hardware. Switching the choice of the underlying
filter allows you to perform experiments that trade hardware cost against speed.
Defining a Configurable Subsystem
A configurable subsystem is defined by creating a Simulink library. The underlying blocks
that implement a configurable subsystem are organized in this library. To create such a
library, do the following:
•
Make a new empty library.
•
Add the underlying blocks to the library.
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•
Drag a template block into the library. (Templates can be found in the Simulink library
browser under Simulink/Ports & Subsystems/Configurable Subsystem.)
•
Rename the template block if desired.
•
Save the library.
•
Double click to open the template for the library.
•
In the template GUI, turn on each checkbox corresponding to a block that should be
an implementation.
•
Press OK, and then save the library again.
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Configurable Subsystems and System Generator
Using a Configurable Subsystem
To use a configurable subsystem in a design, do the following:
•
As described above, create the library that defines the configurable subsystem.
•
Open the library.
•
Drag a copy of the template block from the library to the appropriate part of the
design.
•
The copy becomes an instance of the configurable subsystem.
•
Right-click on the instance, and under Block choice select the block that should be
used as the underlying implementation for the instance.
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Deleting a Block from a Configurable Subsystem
To delete an underlying block from a configurable subsystem, do the following:
•
Open and unlock the library for the subsystem.
•
Double click on the template, and turn off the checkbox associated to the block to be
deleted.
•
Press OK, and then delete the block.
•
Save the library.
•
Compile the design by typing Ctrl-d.
•
If necessary, update the choice for each instance of the configurable subsystem.
Adding a Block to a Configurable Subsystem
To add an underlying block to a configurable subsystem, do the following:
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•
Open and unlock the library for the subsystem.
•
Drag a block into the library.
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Configurable Subsystems and System Generator
•
Double click on the template, and turn on the checkbox next to the added block.
•
Press OK, and then save the library.
•
Compile the design by typing Ctrl-d.
•
If necessary, update the choice for each instance of the configurable subsystem.
Generating Hardware from Configurable Subsystems
In System Generator, blocks both participate in simulations and produce hardware.
Sometimes, for a configurable subsystem, it is worthwhile to use one underlying block for
simulation, but use another for hardware generation. For example, it might make sense to
use ordinary System Generator blocks to produce simulation results, but use a black box to
supply the corresponding HDL. The System Generator configurable subsystem manager
block makes this possible; the ordinary block choice for the configurable subsystem is used
when simulating, and the block specified in the manager is used for hardware generation.
To use a configurable subsystem manager, do the following:
•
Open and unlock the library for the configurable subsystem.
•
Select one of the blocks in the library, and double click to open it. (Aside from the
template any block will do, provided the block is itself a subsystem. If there is no such
subsystem in the library, it is not possible to use a configurable subsystem manager.)
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•
Drag a manager block into the subsystem opened above. (The manager block can be
found in Xilinx Blockset/Tools/Configurable Subsystem Manager).
•
Double click to open the GUI on the manager, then select the block that should be
used for hardware generation in the configurable subsystem.
•
Press OK, then save the subsystem, and the library.
The Mathworks description of configurable subsystems can be found the following
address:
http://www.mathworks.com/access/helpdesk/help/toolbox/simulink/slref/configura
blesubsystem.shtml.
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Notes for Higher Performance FPGA Design
Notes for Higher Performance FPGA Design
When you use the following design practices, it helps System Generator produce efficient
and high performance hardware realizations.
Review the Hardware Notes Included in Block Dialog Boxes
Pay close attention to the Hardware Notes included in the block dialog boxes. Many blocks
in the Xilinx Blockset library have notes that explain how to achieve the most hardware
efficient implementation. For example, the notes point out that the Scale block costs
nothing in hardware. By contrast, the Shift block (which is sometimes used for the same
purpose) can use hardware.
Register the Inputs and Outputs of Your Design
Register inputs and outputs of your design. This can be done by placing a Delay block
having latency 1 or a Register block after the Gateway In and before Gateway Out blocks.
Selecting any of the Register block features adds hardware.
Double registering the I/Os may also be beneficial. This can be performed by instantiating
two separate Register blocks, or by instantiating two Delay blocks, each having latency 1.
This allows one of the registers to be packed into the IOB and the other to be placed next to
the logic in the FPGA fabric. A Delay block with latency 2 does not give the same result
since this block is implemented using an SRL16 and cannot be packed into an IOB.
Insert Pipeline Registers
Insert pipeline registers wherever possible. Deep pipelines are efficiently implemented
with the Delay blocks since the SRL16 primitive is used. If an initial value is needed on a
register, the Register block should be used.
Use Saturation Arithmetic and Rounding Only When Necessary
Saturation arithmetic and rounding have area and performance costs. Use only if
necessary.
Use the System Generator Timing Analysis Tool
Use System Generator Timing Analysis Tool to Meet Timing Requirements. System
Generator provides a Timing Analysis tool that can help resolve timing related issues. The
timing analysis tool shows you the slowest paths and those paths which are failing to meet
the timing requirements. For more information refer to topic Timing Analysis
Compilation.
Set the Data Rate Option on All Gateway Blocks
Select the IOB timing constraint option Data Rate on all Gateway In and Gateway Out
blocks. When Data Rate is selected, the IOBs are constrained at the data rate at which the
IOBs operate. The rate is determined by the Simulink system period(sec) field in the
System Generator block and the sample rate of the Gateway relative to the other sample
periods in the design.
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Reduce the Clock Enable (CE) Fanout
An algorithm in the ISE Mapper uses register duplication and placement based on
recursive partitioning of loads on high fanout nets. This means improved FMAX on
System Generator designs with large CE fanout.
Although this feature is enabled in System Generator by default, the fanout reduction
occurs downstream during the ISE mapping operation and the following MAP options
must be turned on:
•
Perform Timing-Driven Packing and Placement : on
•
Map Effort Level : High
•
Register Duplication : on
If you are using the ISE Project Navigator flow, these MAP options are also on by default.
However, if you are using a System Generator flow like Bitstream, you must turn on these
MAP options by modifying the bitstream .opt file or by providing you own .opt file. See
the topic XFLOW Option Files for more information.
Another method is to select the Clock Generator (DCM) clocking option or the Expose
Clock Ports clocking option on the System Generator Token.
Processing a System Generator Design with FPGA Physical
Design Tools
HDL Simulation
System Generator creates custom .do files for use with your generated project and a
ModelSim simulator. To use these files, you must have ModelSim (PE or EE/SE) or the
Xilinx Edition of ModelSim (MXE). You may run your simulations from the standalone
ModelSim tool, or you may associate it with the Xilinx ISE Project Navigator, and run your
simulations from within Project Navigator as part of the full software implementation
flow.
Compiling Your IP
Before you can simulate your design, you must compile your IP (cores) libraries with
ModelSim.
ModelSim (PE or EE/SE)
There are multiple ways to compile your IP libraries. Complete instructions for running
compxlib can be found in Chapter 25 of the the Xilinx Development System Reference
Guide.
From the Windows command line you can compile the necessary HDL libraries using the
compxlib program. For example, the following command can be used to compile all the
HDL libraries with ModelSim SE:
compxlib -s mti_se -f all -l all
xlDoc
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If you plan to use ModelSim XE (Xilinx Edition), download the MXE pre-compiled
libraries from the Xilinx web site. The latest libraries are located at:
http://www.xilinx.com/ise/optional_prod/mxe.htm
Unzip these MXE libraries into your MXE installed directory, e.g.: C:/Modeltech_XE/.
This is the location where MXE expects to find your Xilinx compiled libraries, so you do
not need to make any changes to your modelsim.ini file. This file should point to the
correct installed location.
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Simulation using ModelSim within Project Navigator
Before you can launch ModelSim from Project Navigator you must specify the location of
your installed version of ModelSim (either MXE or ModelSim EE/SE/PE). To do so, open
Project Navigator and choose the main menu Edit > Preferences. This brings up a dialog
box. Choose the ISE General > Integrated Tools category in the dialog box. Enter the full
path to the version of ModelSim on your PC in the Model Tech Simulator edit box. You
must include the name of the executable file in this field.
The Project Navigator project is already set up to run simulations at four different stages of
implementation. System Generator creates four different ModelSim .do files when the
Create Testbench option is selected on the System Generator block. The ModelSim do files
created by System Generator are:
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•
pn_behavioral.do - for a behavioral (HDL) simulation on the HDL files in the
project, before any synthesis or implementation.
•
pn_posttranslate.do - this file runs a simulation on the output of the Xilinx
translation (ngdbuild) step, the first step of implementation.
•
pn_postmap.do - to run a simulation after your design has been mapped. This file
also includes a back-annotated simulation on the post-mapped design.
•
pn_postpar.do - to run a simulation after your design has been placed and routed.
This file also includes a back-annotated simulation step.
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Processing a System Generator Design with FPGA Physical Design Tools
In the Project Navigator Sources window, use the pull-down menu labeled Sources for
to select Behavioral Simulation, Post-Translate Simulation, Post-Map Simulation, or PostRoute Simulation (corresponding to pn_behavioral.do, pn_posttranslate.do,
pn_postmap.do, and pn_postpar.do respectively).
If you select the <your design>_tb.vhd/.v file in the Project Navigator Sources
window, the ModelSim Simulator will become available in the Process window. Expand
the ModelSim Simulator process by clicking on the plus button to the left of it. A
simulation process associated with the ModelSim Simulator will appear (in the image
below the process is labeled Simulate Behavioral Model).
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The Process Properties dialog box shows that the System Generator.do file is already
associated as a custom file for this process.
Now if you double-click on the simulation process, the ModelSim console opens, and the
associated custom do file is used to compile and run your System Generator testbench. The
testbench uses the same input stimuli that was generated in Simulink, and compares the
HDL simulation results with the Simulink results. Provided that your design was error
free, ModelSim reports that the simulation finished without errors.
Generating an FPGA Bitstream
Xilinx ISE Project Navigator
During code generation, the System Generator creates several project files for use in Xilinx
and partner software tools. One of these project files is for the Xilinx ISE Project Navigator
tool. By opening this project file, you can import your System Generator design into the
Project Navigator, and from there, you can synthesize, simulate, and implement the
design. This file is called <design_name>_cw.ise and it is created in the target directory
specified in the System Generator block.
Note: my_project_cw.ise is used in the following discussion.
Opening a System Generator Project
You may double-click on your .ise file in Windows Explorer. The Project Navigator file
association with .ise causes Project Navigator to launch, opening your
my_project_cw.ise System Generator design project. You may also open the Project
Navigator tool directly, then choose File > Open Project from the top-level pull down
menu. Browse to the location of your System Generator my_project_cw.ise and open
it.
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Customizing your System Generator Project
When first opening your System Generator project, you will see that it has been set up with
the synthesis tool, device, package, and speed grade that you specified in the System
Generator block. To change these settings, open the Project Navigator properties dialog,
right-click on the device and default package at the top of the sources window, and select
Properties.
This brings up the Project Properties window. From this window, you can change your
part, package, speed, and synthesis compiler. Note that if you change the device family, the
Xilinx IP cores that were produced by System Generator must be regenerated. In such a
case, it is better if you return to the System Generator and re-generate your project.
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Implementing Your Design
You have many options within Project Navigator for working on your project. You can
open any of the Xilinx software tools such as the Floorplanner, Constraints Editor, report
viewers, etc. To implement your design, you can simply instruct Project Navigator to run
your design all the way from synthesis to bitstream. In the Sources window, select the toplevel HDL module in your design. In our example the top-level HDL module is named
my_project_cw - structural. The Processes window shows the processes that can
be run on the top-level HDL module.
In the Processes window, if you right-click on Generate Programming File and select Run,
you are instructing Project Navigator to run through whatever processes are necessary to
produce a programming file (FPGA bitstream) from the selected HDL source. In the
messages console window, you see that Project Navigator is synthesizing, translating,
mapping, routing, and generating a bitstream for your design.
Now that you have generated a bitstream for your design, you have access to all the files
that were produced on the way to bitstream creation.
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Resetting Auto-Generated Clock Enable Logic
Resetting Auto-Generated Clock Enable Logic
System Generator provides a bit and cycle accurate modeling of FPGA hardware in the
Simulink environment. Several clocking options are available including the default option
Clock Enables. With this option, System Generator uses a single clock accompanied by
clock enables (ce) to keep various sample domains in sync. Multirate clocking is described
in detail in the topic Compilation Results. System Generator models are often included as
part of a bigger system design which need dynamic control for specifying the beginning of
data path sampling. To allow this control within a bigger framework System Generator
block provides an optional ce_clr port in the top-level HDL clock wrapper for resetting
the clock enable generation logic. The figure below shows the reset of the CE4 signal
generation logic after ce_clr signal is de-asserted.
The effect of ce_clr signal cannot be simulated using the original System Generator
design. To model this behavior within Simulink follow the steps below:
1.
Select Provide clock enable clear pin and NGC Netlist Compilation option on the
System Generator block.
2.
Press the Generate button on the System Generator block.
3.
Run the following command from the MATLAB console to produce the post translate
VHDL netlist. Use “-ofmt verilog” with netgen for generating Verilog netlist:
>> !netgen -ofmt vhdl ./<target_directory>/<design_name>_cw.ngc
4.
Bring in the post translate VHDL/Verilog file as a Black Box within Simulink and use
HDL co-simulation to model the effect of asserting ce_clr signal on your design.
ce_clr and Rate Changing Blocks
The ce_clr signal changes the sampling phase of all the multi-sample data signals. This
behavior has the potential of changing the functionality of all rate changing blocks which
rely heavily on the ce signal to have a periodic occurrence. The various rate changing
blocks and their behavior with regards to the de-assertion of the ce_clr signal is
explained in the table below. These blocks were characterized by importing and simulating
the post translate HDL model as a black box.
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Block Name
96
Synchronized to
ce after ce_clr
Behavior after ce_clr is de-asserted
Synchronized
deasserted
and the next ce pulse
to ce_clr
( 1 sample cycle
delay)
Down Sampler
with Last Value
of frame
Yes
N/A
The last sampled value is held till the
new ce signal arrives.
Down Sampler
with First Value
of frame
No
No
Re-synchronization does not occur
after de-assertion of the ce_clr signal.
Up Sampler
with copy
samples
Yes
N/A
In hardware, this block is
implemented as a wire.
Up Sampler
with zeros
inserted
No
Yes
The last value (zero or sample) is held
till the next destination ce signal
arrives.
Time Division
Multiplexer
No
Yes
The TDM block samples through all
the remaining input channels and
then sets the output to 0 till the next ce
arrives. The new ce signal resynchronizes the output to the new
frame definition.
Time Division
Demultiplexer
No
Yes
The TDD block holds the output
channels to the same value till the
next ce signal arrives. The new ce
signal re-synchronizes the output to
the new frame definition.
Parallel to Serial
No
Yes
The p2s block samples through all the
remaining data words and then holds
the output to the last sampled word
until the next ce arrives. The new ce
signal starts the conversion of the
parallel data stream to a serial one.
Serial to Parallel
No
Yes
The s2p block holds the output when
the ce_clr is asserted. When deasserted, the input is sampled on the
last value of the input sample frame,
and the output occurs on the first ce
pulse corresponding to the output
rate.
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Resetting Auto-Generated Clock Enable Logic
Block Name
Addressable
Shift Register
(ASR)
Polyphase FIR
Synchronized to
ce after ce_clr
Synchronized
Behavior after ce_clr is de-asserted
deasserted
to ce_clr
and the next ce pulse
( 1 sample cycle
delay)
No
No
Yes
The ASR block will hold the values in
the shift register when ce_clr is
asserted. When de-asserted, the
stored values will be shifted out, and
new data will be put into the shift
register.
No
Interpolating or Decimating FIR does
not work with the ce_clr signal unless
the optional reset port is used to reset
the FIR after the ce_clr is de-asserted.
ce_clr Usage Recommendations
•
Based on the above analysis, the ce_clr signal can be used if the following
recommendations are adhered to:
•
Replace down sampler blocks with first value of frame behavior with an equivalent
circuit using down sampler block with last value of frame selected.
•
Design for N clock cycles of invalid data after ce_clr is de-asserted, where N is the
slowest ce associated with the block.
•
Design the model to always use down sampler with last value of frame and up
sampler with copy samples.
•
If N cycle invalid data is not desired replace parallel to serial, serial to parallel, time
division multiplexer and time division demultiplexer block with an equivalent circuit
built out of a counter, mux and up/down sampler blocks. The equivalent design
circuit should also have a reset port pulled to the top-level and connected to the same
signal driving the ce_clr port.
•
Counters used in performing operations like multiply-accumulate should always be
reset using a combination of user reset which is tied to the ce_clr signal and ce
signal extracted from the Clock Enable Probe block.
•
Always verify the effect of ce_clr signal on the design by importing and simulating
the post translate HDL model as a black box.
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Design Styles for the DSP48
About the DSP48
Xilinx Virtex-4 and Virtex-5 devices offer an efficient building block for DSP applications
called the DSP48 (also known as the Xtreme DSP Slice). The DSP48 is available as a System
Generator block which is a wrapper for the DSP48 UNISIM primitive. Architectural and
usage information for this primitive can be found in the DSP48 Users Guide in the Virtex4 data book. The DSP48 is available in all Virtex-4 devices and is featured in the SX series
devices which contain up to 512 DSP48 blocks.
B, BCIN
BCOUT
18
18
A
P, PCOUT
18
48
PCIN
48
C
48
Op
11
to various
control ports
= optional register with
optional reset and
clock enable
The DSP48 combines an 18-bit by 18-bit signed multiplier with a 48-bit adder and a
programmable mux to select the adder's inputs. It implements the basic operation: "p=a*b
+(c+cin);", however other operations can be selected dynamically. Optional input and
multiplier pipeline registers are also included and must be used to achieve maximum
speed. Also included with the DSP48 are high performance local interconnects between
adjacent DSP48 blocks (BCIN-BCOUT and PCIN-PCOUT). The DSP48 also includes
support for symmetric rounding. This combination of features enables DSP systems which
use the higher-speedDSP48 devices to be clocked at over 500 MHz.
There are three ways to program a DSP48 in System Generator:
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Use Standard Components - Map designs to Mult and AddSub blocks or use higherlevel IP such as the MACFIR filter generator blocks. This approach is useful if the
design needs to be compatible with V2P or S3 devices or uses a lower-speed clock and
the mapping to DSP48s is not required.
•
Use Synthesizable Blocks - Structure the design to map onto the DSP48's internal
architecture and compose the design from synthesizable Mult, AddSub, Mux and
Delay blocks. This approach relies on logic synthesis to infer DSP48 blocks where
appropriate. This approach gives the compiler the most freedom and can often
achieve full-rate performance.
•
Use DSP48 Blocks - Use System Generator's DSP48 and DSP48 Macro blocks to
directly implement DSP48-based designs. This is the highest performance design
technique. Be aware however that obtaining maximum performance and minimum
area for designs using DSP48s may require careful mapping of the target algorithm to
the DSP48's internal architecture, as well as the physical planning of the design.
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Designs Using Standard Components
Designs for Xilinx FPGAs such as Virtex2P and Spartan3 will compile to the Virtex-4
devices. Multipliers will be mapped into the DSP48 block, however, logic synthesis tools
cannot pack adders and muxes into the DSP48 block since these blocks are delivered as
cores which prevents synthesis from optimizing the logic. Place and route tools do place
the MULT18x18S and MULT18x18 into the DSP48 block but do not pack the adder, or mux
into the DSP48 block. (PAR will however pack the mux into the LUT-based adder).
To obtain the best possible performance, you should set the multiplier latency to 3 and
include an input register to cover the delay from the DSP48's output to the adder. The
performance of this circuit is in the 200-300 MHz range with V-44-11 devices, and is limited
by the adder speed. In Virtex-4, unlike V2P and S3 devices, the multiply speed in nearly
independent of bit width. For medium speed designs, this approach works fine.
An additional way to use the DSP48 is to use IP blocks optimized for the DSP48 such as the
MACFIR block available from coregen, or to use the architecture wizard to generate a
custom configured DSP48. Both of these approached require importing the logic
containing the DSP48 as a black box into System Generator. Simulation will require
modelsim HDL cosim.
Designs Using Synthesizable Mult, Mux and AddSub Blocks
Synthesis tools now have the ability to infer DSP48 logic. This enables the tools to pack
adders, multipliers and muxes into the DSP48 block, as well as to enable the application of
retiming and other synthesis techniques such as register duplication.
If the design is composed of synthesizable blocks, both Synplify Pro and XST have
demonstrated the ability to infer DSP48s and to make use of the DSP48's local interconnect
buses (PCOUT-PCIN and BCOUT-BCIN). In the above example, three blocks have been
built using the MCode blocks which are defined by the following M-functions.
function o = xlsynmux2(i0,i1,sel)
if (sel==0) o=i0; else o=i1; end
function p = xlsynmult(a,b)
p=a*b;
function s = xlsynadd(a,b)
s=a+b;
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For synthesis to work, the circuit must be mappable to the DSP48 and signal bitwidths
must be less than the equivalent buses in the DPS48.
You should kept in mind that the logic synthesis tools are rapidly evolving and that
inferring DPS48 configurations is more of an art than a science. This means that some
mappable designs may not be mapped efficiently, or that the mapping results may not be
consistent. It will be necessary to inspect the post synthesis netlist using a tool similar to
Synplify Pro's gate-level technology viewer to determine if the design is being correctly
mapped. If not, it may be possible to recast it to be correctly inferred. A model of a fully
synthesizable FIR filter is located at the follwing pathname in the System Generator
software tree:
.../sysgen/examples/dsp48/synth_fir/synth_fir_tb.mdl
Designs that Use DSP48 and DSP48 Macro Blocks
DSP48 Block
The DSP48 block is effectively a wrapper for the DSP48 UNISIM primitive. Because of this,
any possible DSP48 design can be implemented. This low-level implementation however
requires an 11-bit binary opmode to be routed to the DSP48's control ports in order to
configure its function. The Constant block has a special mode enabling it to generate a
DSP48 control field. The DSP48's parameters dialog box is used to configure the pipelining
mode of the DSP48 as well as the use of the DSP48's local interconnect buses named
PCOUT-PCIN and BCOUT-BCIN. You can try out the DSP48 block by opening the
simulink model that is located at the follwing pathname in the System Generator software
tree:
.../sysgen/examples/dsp48/dsp48_primitive.mdl
Dynamic Control of the DSP48
The DSP48 has the unique capability of being able to change its operation on a per cycle
basis. This is useful in applications where the DSP48 is used in a 'resource shared' mode
such as a FIR filter where multiple taps are implemented by the same multiplier. A simple
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method of generating this type of control pattern is to use a mux to select the DSP48
instruction on a clock by clock basis.
The above example illustrates the use of a DSP48 and Constant blocks to implement a 35bit by 35-bit multiplier over 4 clock cycles. During synthesis, the mux and constant logic is
reduced by logic optimization. In the example above, the DSP48 block and the 4:1 mux are
reduced to just two 4-LUTs. A Simulink model that illustrates how to implement both
parallel and sequential 35*35-bit multipliers using dynamic operation for the sequential
mode of operation is located at the follwing pathname in the System Generator software
tree:
.../sysgen/examples/dsp48/mult35x35/mult35x35_tb.mdl
DSP48 Macro Block
The DSP48 Macro block is a wrapper for the DSP48 block which makes it simple to
implement a sequence of DSP48 instructions (known as dynamic instructions). In addition,
it provides support for specifying input and output types. For example, in the model
above, a DSP48 Macro block is configured to implement a complex multiplier using a
sequence of four different instructions. The instructions are entered in a text window in the
DSP48 Macro's dialog menu. You can try out the DSP48 Macro block by opening the
simulink model that is located at the follwing pathname in the System Generator software
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tree:
.../sysgen/examples/dsp48/dsp48_macro.mdl
DSP48 Design Techniques
Designing Filters with the DSP48
The DSP48 is an ideal block to implement FIR filters. You can examine how to use the
DSP48 block for Type 1 and Type 2 FIR filters by opening the simulink model that is located
at the follwing pathname in the System Generator software tree:
.../sysgen/examples/dsp48/firs/dsp48_firs_tb.mdl
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Design Techniques for Very-High Performance Designs
DSP48-based designs usually require I/O, BRAMS and SLICE logic. Typically, this
associated SLICE logic is used to implement delay registers, SRL16s, muxes, counters, and
control logic. Since the DSP48 block is expected to operate at speeds greater than 500 MHz,
other components will also be required to operate at the same speed. This generally
requires special design techniques for the non-DSP48 logic.
At 500 MHz only 2 ns is available in each clock. For V4-11 devices, roughly 300 ps are
required for register clock to out and 300 ps for setup. For comparison, a LUT delay is 166
ps. Special inputs and outputs such as clock enables and DSP48 and BRAM signals
generally have setup and clock to out times closer to 500 ps. With clock skew and jitter,
roughly 1 ns is available for net delays. This restriction will generally allow only 1 net in
each path and it must be fairly short.
There are a number of guidelines that can be used to insure the operation at DSP48 speeds.
Some of these guidelines are outlined below.
8) srl16 as control pattern
generator
9) dsp48 as counter, adder
SRL16
BRAM
5) Limit fanout to 4-8
loads
DSP48
2) Extra output regs
+
1) Pipeline regs
BRAM
lut
+
6) Use input and
output regs with
7) Limit to 1 level
LUTs
of logic
+
3) PCOUT-PCIN
b
1) use input and output regs
4) Use extra registers to cover distance greater than 20-40 slices
1.
Always use DSP48, BRAM16, FIFO16 with input, mult and output registers
2.
Use additional FF to buffer DSP48 and BRAM outputs if necessary
3.
Plan out the usage of the PCOUT-PCIN bus to allow DSP48 chaining
4.
Add registers to any path that is greater than 20 - 40 slices long
5.
Limit fanout to 32 loads located within a 20 slice distance
6.
Add output registers to any LUT-based logic
7.
Limit LUTs to 1 level or a 4:1 MUX and insure a local register for input or output
8.
Use RAMs, SRL16 to clock out control patterns instead of state machines
9.
Use DSP48 to implement counters and adders greater than 8-16 bits
10. Use area constraints – "INST ff1* LOC = SLICE_X0Y8:SLICE_X1Y23;"
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Physical Planning for DSP48-Based Designs
The DSP48 requires correct placement to achieve dense, high performance designs. While
the automatic place and route tools do a good job, the best results may require manual
placement of DSP48 and RAM blocks. There are several additional issues with the DSP48s.
Cascade Routing Buses
Adjacent DSP48 blocks are connected with two local buses called PCOUT, and BCOUT.
The PCOUT bus is used to pass accumulation data from one DSP48 to the next. The
BCOUT bus is used to pass delayed B input data to the next DSP48. The DSP48 and DSP48
Macro block both support PCOUT and BCOUT buses. The use of the buses is shown in the
figure above, which illustrates a pipelined 4-Tap Type 1 FIR filter.
C-Input Sharing
Each pair of DSP48s share a single C input. You should be aware of this when you do
resource planning. Since the placer will not always find the most optimal placement to
share C inputs, DSP48s should avoid using C inputs if possible.
Adder Trees Planning
Tree-based filter topologies are problematic for efficient DSP48 implementation. An adder
tree requires isolated 2-input adders. Two input 36-bit adders can be implemented using a
single DSP48, however this requires a C input and precludes the use of the multiplier. In
addition, the long signals between DSP48s may require additional pipeline stages. A better
approach is to convert the tree into a pipelined cascade.
Placement
Most designs will benefit from some placement of DSP48 and BRAMs. Use of area
constraints to constrain LUT fabric logic placement may also be beneficial.
Signal Length Planning
At 500 MHz, signal lengths should be limited to around 20 slices. This means that long
signals should have multiple pipeline stages.
Clock Enable Planning
When using the Clock Enables clocking option, the clock enables are often the limiting
path at high frequencies. This is partially due to System Generator's use of LUTs to gate
clocks at the destination. To avoid clock enables in the critical path, avoid using the System
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Generator upsampled and downsampled clock domains. This requires the manual use of
clock enables for logic that runs at less than the system clock rate.
Place and Route Flow
•
Use the command map -timing with effort level high for both map and place
•
Use trce –v 100 to get a good sense of the failing nets and inspect the
xflow/design.twr file to understand the nature of the design's timing.
•
The file bitstream_v4.opt is available in the examples/dsp48 directory. This
file can be used with the Bitstream compile target to set the PAR options mentioned
above.
Synthesis Flow
•
Use Synplify Pro with retiming and pipelining enabled to avoid having to manually
pipeline every LUT and signal.
•
Use Synplify Pro with the fanout limit set around 32 to avoid long net delays.
•
Open compiled projects in Synplify Pro and inspect the generated logic using the
RTL- and Gate-level views to get a good idea of what logic is being generated.
•
The file syn.pl is available in the examples/dsp48 directory. Place this file in
<sysgen_tree>/scripts directory to modify the synthesis options in System
Generator
Logic Depth Planning
The following rules seem to allow the LUT fabric to run at 450 MHz using a -11 V4 device:
•
Only one net can be allowed in a critical path at 450 MHz. This allows a 4:1 mux to a
reg a 4_input LUT to a reg or a net through a LUT directly to a DSP48
•
Counters up to 16-bits can be used, but do not use count limited counters without
additional pipelining
•
If accumulators or counters are used, invert the enable line to an active-low condition
to prevent a extra LUT from being inserted in the critical path
•
Any adders must have local input registers. It may be necessary to place control
counters in the DSP48 to insure speed.
Fanout Planning
Avoid fanouts of more than 32 LUTs or 8 DSP48s or BRAMs. This can be avoided by
inserting additional pipeline registers in these signals paths.
Register Retiming
Check retiming on delay blocks to allow them to be used as registers for pipelining. Then
use Synplify Pro or XST with retiming enabled to allow the synthesis tool to move registers
into optimal positions.
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Using FDATool in Digital Filter Applications
The following example demonstrates one way of specifying, implementing, and
simulating a FIR filter using the FDATool block. The FDATool block is used to define the
filter order and coefficients and the Xilinx Blocksets are used to implement a MAC-based
FIR filter using a single MAC (Multiply-ACcumulate) engine. The quality of frequency
response is then validated by comparing it to a double-precision Simulink filter model.
Although a single MAC engine FIR filter is used for this example, we strongly recommend
that you look at the DSP Reference Library provided as a part of the Xilinx Reference
Blockset. The DSP Reference Library consists of multi-MAC, as well as, multi-channel
implementation examples with variations on the type of memory used.
A demo included in the System Generator demos library also shows an efficient way to
implement a MAC-based interpolation filter. To see the demo, type the following in the
MATLAB command window:
>> demo blockset xilinx
then select FIR filtering: Polyphase 1:8 filter using SRL16Es from the list of demo designs.
Design Overview
This design uses the random number source block from the DSP Blockset library to drive
two different implementations of a FIR filter:
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The first filter is the one that could be implemented in a Xilinx device. It is a fixedpoint FIR filter implemented with a dual-port Block memory and a single multiplyaccumulator.
•
The second filter is what is refered to as reference filter. It is a double-precision, directform II transpose filter.
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The frequency response of each filter is then plotted in a transfer function scope.
Open and Generate the Coefficients for this FIR Filter
1.
From the MATLAB console window, cd into the directory
<sysgen_tree>/sysgen/examples/mac_fir.
2.
Open the design model by typing mac_df2t from your MATLAB command window.
For the purpose of this tutorial, the variables coef, coef_width, coef_binpt,
data_width, data_binpt and Fs are not defined. You will first use these variables as
mask parameters to the MAC block and then design and assign the filter coefficients using
the FDATool. The fully functional model is available in the current directory and is called
mac_df2t_soln.mdl.
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Parameterize the MAC-Based FIR Block
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1.
Right Click on the MAC-Based FIR block and select Edit Mask as shown in the figure
below.
2.
Add the parameters coef, data_width and data_binpt as shown below.
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Generate and Assign Coefficients for the FIR Filter
3.
Drag and drop the FDATool block in your model from the DSP Xilinx Blockset Library.
4.
Double-click on the FDATool block and enter the following specifications in the Filter
Design & Analysis Tool for a low-pass filter designed to eliminate high-frequency
noise in audio systems:
5.
♦
Sampling frequency: Fs = 44.1 KHz
♦
Passband frequency: Fpass = 6 KHz
♦
Stopband frequency: Fstop = 7.725 KHz
♦
Passband ripple: Apass = 1dB
♦
Stopband ripple: Astop = 48 dB
Click on Design Filter at the bottom of the tool window to find out the filter order and
observe the magnitude response.
You can also view the phase response, impulse response, coefficients and more by
selecting the appropriate icon at the top-right of the GUI. Based on the FDATool, a 43tap FIR filter is required in order to meet the design specifications listed above.
The filter coefficients can be displayed in the MATLAB workspace by typing:
>> xlfda_numerator('FDATool')
These useful functions help you find the maximum and minimum coefficient value in
order to adequately specify the coefficient width and binary point:
>> max(xlfda_numerator('FDATool'))
>> min(xlfda_numerator('FDATool'))
For this tutorial, the coefficient type has been set to be Fix_12_12, which is a 12-bit
number with the binary point to the left of the twelfth bit. The result of the max()
function above shows that the largest coefficient is 0.3022, which means that the binary
point may be positioned to the left of the most significant bit. How do you reason that?
A Fix_12_12 number has a range of -0.5 to 0.4998, meaning the dynamic range is
maximized by putting the binary point left of the most significant bit. If you moved the
binary point to the right (by using a Fix_12_11 number) you would lose one bit of
dynamic range because a Fix_12_11 number has a range of -1 to 0.9995, which is more
than you require to represent the coefficients.
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6.
Enter the parameter values for coef, coef_width, coef_binpt, data_width, data_binpt
and Fs as shown below.
In order to be able to preload the coefficients without having to regenerate them with
the FDA Tool each time, the mac_df2t.mdl simulink model is opened, you are now
going to save it into a file.
Browse Through and Understand the Xilinx Filter Block
The following block diagram showing how the MAC-based FIR filter has been
implemented for this tutorial.
At this point, the MAC filter is set up for a 10-bit signed input data (Fix_10_8), a 12-bit
signed coefficient (Fix_12_12), and 43 taps. All these parameters can be modified directly
from the MAC block GUI. The coefficients and data need to be stored in a memory system.
For the tutorial, you choose to use a dual-port memory to store the data and coefficients,
with the data being captured and read out using a circular RAM buffer. The RAM is used
in a mixed-mode configuration: values are written and read from port A (RAM mode), and
the coefficients are only read from port B (ROM mode).
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The multiplier is set up to use the embedded multiplier resource available in Xilinx VirtexII and Virtex-II Pro devices as well as three levels of latency in order to achieve the fastest
performance possible. The precision required for the multiplier and the accumulator is a
function of the filter taps (coefficients) and the number of taps. Since these are fixed at
design time, it is possible to tailor the hardware resources to the filter specification. The
accumulator need only have sufficient precision to accumulate maximal input against the
filter taps, which is calculated asa follows:
acc_nbits = ceil(log2(sum(abs(coef*2^coef_width_bp)))) + data_width+ 1;
Upon reset, the accumulator re-initializes to its current input value rather than zero, which
allows the MAC engine to stream data without stalling. A capture register is required for
streaming operation since the MAC engine reloads its accumulator with an incoming
sample after computing the last partial product for an output sample.
Finally, a downsampler reduces the capture register sample period to the output sample
period. The block is configured with latency to obtain the most efficient hardware
implementation. The downsampling rate is equal to the coefficient array length.
Run the Simulation
When you run the simulation you will get the following message as shown in the figure
below. System Generator gets its input sample period from the din Gateway In block
which has 1/Fs specified as the data input sample period. As the MAC-based FIR filter is
oversampled according to the number of taps, the System Clock Period would always be
equal to 1/(Filter Taps * Fs). Click on Update to specify the System Clock Period as
5.273427e-007 = 1/(43 * 44100).
You can now run the simulation and notice that the Xilinx implementation of the MACbased FIR filter meets the original filter specifications and that its frequency response is
almost identical to the double precision Simulink models.
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As you can see, the filter passband response measurement as well as zeros can clearly be
seen. Your FIR filter is perfect!
It is possible to increase or decrease the precision of the Xilinx Filter in order to reach the
perfect area/performance/quality trade off required by your design specifications.
Stop the simulation and modify the data width to FIX_8_6 and the coefficient width to
FIX_10_10 from the block GUI. Update the model (Ctrl-d) and push into the MAC
engine block. You should now notice that the datapath has been automatically updated to
only eighteen bits on the output of the multiplier and twenty on the output of the
accumulator.
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Restart the simulation and observe how the frequency response has been affected. The
attenuation has indeed degraded (less than 40dB) due to the fixed-wordlength effects.
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Generating Multiple Cycle-True Islands for Distinct Clocks
System Generator's shared memory interfaces allow you to implement designs that are
driven by multiple-clock sources. These multi-clock designs may employ a combination of
distinct clocks and derived clock enables to implement advanced clocking strategies
completely within a single design environment. This topic describes how to implement
multi-clock designs in System Generator through discussions of the following topics:
•
Applications that benefit from multiple clocks;
•
Using hierarchy to partition a System Generator model into two or more clock
domains;
•
Using shared memories to cross clock domains;
•
Simulating and netlisting multiple clock designs;
•
Wiring multiple clock domains together using the Xilinx Multiple Subsystem
Generator block.
A step-by-step example is provided to help clarify the topics listed above. Although the
example uses two clocks, the concepts presented here can be extended so that System
Generator designs requiring any number of clock sources can be constructed using similar
techniques.
Before continuing with the example, you may want to familiarize yourself with standard
System Generator clocking terminology and implementation methodologies. This
information is covered in-depth in the topic Timing and Clocking. In general, System
Generator designs are driven by a single, system clock source. Multirate design portions
are handled using clock enables derived from the system clock source. It is possible,
however, to use System Generator to implement designs that are driven by distinct clock
sources.
Broadly speaking, the approach is the following:
Divide the design into several subsystems, each of which is to be driven by a different
clock. In the example, you call these subsystems asynchronous clock islands. Xilinx shared
memory blocks should be used as bridges that communicate between these clock islands.
Once the design is partitioned, the Xilinx Multiple Subsystem Generator block may be
used to translate the design into hardware that uses multiple distinct clock sources.
Multiple Clock Applications
A common application for multiple clock domains is for interfacing different pieces of
external hardware that operate at different clock rates. For example, you may need to
provide a set of I/O registers to a microprocessor, and the processor must be able to read
and write these registers synchronous to its own clock. You may get data from a clock/data
recovery unit and need to re-synchronize the data to your local clock domain. You may
need to feed data to a digital-to-analog converter that must be running at a precise sample
rate which is different from your system clock.
Another important application for multiple clock domains is in employing a high-speed
processing unit. Let us take an example of an interpolating FIR filter. The filter gets symbol
data from an external unit, and the filter needs to take the symbols and perform a 4X
interpolation that creates four output samples for each input symbol. The output samples
are fed to a digital-to-analog converter (DAC) that is clocked at the sample rate.
The FIR filter may be clocked at any of several rates. It may be clocked at the symbol rate,
and on each cycle it must create four samples which will then be fed to the DAC at the
sample rate. This highly parallel implementation has large hardware resource
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requirements and would only be employed if the sample rate were very fast. An
alternative approach is to clock the FIR filter at the sample rate, creating one sample per
cycle. This scenario takes an intermediate amount of hardware and would be used for
intermediate sample rates. If the sample rate is slow, the FIR filter may be clocked at a rate
several times faster than the sample rate, perhaps by means of a DCM that multiplies the
sample-rate clock. In this way the multiplier-accumulator units of the FIR filter may be
reused several times during the calculation of each sample output, requiring the least
amount of hardware. This last method would use a symbol-rate clock domain, a highspeed processing clock domain, and a sample-rate clock domain.
A good FPGA design practice is to have each resource in the FPGA device operating at the
highest possible rate to optimize hardware usage. In general, it is best to use a single clock
domain when possible and to use clock enables to gate slower circuitry, creating multicycle
paths. The drawback to this technique is that it increases power consumption and may
make it difficult to route the high-speed clock enable. As a result, separate domains for
high-speed processing are preferable in some instances. Also, it may not be possible to
avoid dealing with different clock domains when dealing with asynchronous data inputs
and outputs.
Clock Domain Partitioning
Partitioning a multiple-clock design into multiple domains is an important aspect of FPGA
design. System Generator uses design hierarchy to support clock domain partitioning.
More specifically, when a design uses multiple clock domains, the logic associated with
each distinct clock domain should be grouped together in a Simulink subsystem.
The subsystems, or in this case, synchronous islands, are cycle-true in the sense that the
hardware that is generated for an island is faithful to the Simulink behavior of the island
model. The notion of bit and cycle accuracy is preserved only within the individual
synchronous islands. The end model containing the synchronous islands is not necessarily
cycle-true, because it drives the islands with asynchronous clocks. Although System
Generator and Simulink are able to simulate the design using ideal clock sources, the
complexities involved with asynchronous clocking systems can result in discrepancies
between the software simulations and hardware realizations.
The advantages to partitioning a design using subsystems are manifold:
•
The physical clock lines are abstracted away from the block diagram;
•
Cross-domain transfers are well-defined and can be handled with metastable-safe
blocks from the Xilinx Blockset;
•
Because the domains are well-defined, System Generator can accurately produce
timing constraints for the synchronous islands.
The abstraction level of System Generator reduces the risk that users will perpetrate some
of the more common design errors. These include:
•
Gated Clocks: because the clocks in System Generator are inferred during hardware
generation, it is not possible to connect non-clock lines to clock inputs (i.e., gated
clocks).
•
Asynchronous Clears: because the asynchronous resets in System Generator are
inferred during hardware generation, it is not possible to explicitly clear synchronous
logic using the asynchronous reset, which often results in timing problems.
•
Inferred Latches: latches will not be generated from System Generator designs.
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Crossing Clock Domains
System Generator shared memory blocks should be used whenever it is necessary to cross
clock domains. The tool provides several blocks for transferring data across clock domains,
each of which is available in the Xilinx Shared Memory library:
•
Shared Memory
•
To FIFO / From FIFO
•
To Register / From Register
When these shared memory blocks are used to cross clock domains, each set should be
split into a matched pair.
The To FIFO block is put in the domain in which it is to be written. The From FIFO is put
in the domain in which it is to be read. The two blocks are linked by the name of the
Shared memory name parameter. The FIFO is implemented in hardware using the Xilinx
FIFO Generator core. Using FIFO blocks is the safest and easiest-to-use of the three blocks
which cross domains and is the best for high-bandwidth, sequential data transfers.
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A pair of Shared Memory blocks is implemented as embedded Xilinx dual-port block
RAM core. The two blocks are linked by the name of the shared memory object. Each
member of the pair resides in a different domain. Because the RAM is a true dual-port,
each domain may write to the RAM. Care must be taken, by means of semaphores or other
logic, to ensure that two writes or a read and a write to the same address do not happen
simultaneously. For example, if domain A writes to a memory location at the same time
that domain B is reading from it, the data read may not be valid. The shared memory is
implemented as a using Xilinx Dual Port Block Memory core to ensure that large memories
are efficiently mapped across multiple BRAMs.
The To Register is put in the domain in which it is to be written, and the From
Register in the domain from which it is to be read. The two blocks are linked by the
name of the shared memory. The To Register may also be read synchronously in its own
domain. The register may be of variable width and will synthesize as flip-flops. A 1-bit
To/From Register pair will synthesize as a single flop.
Note: Crossing domains in this manner can be unsafe, and requires the use of metastabilityreducing synchronization flops and semaphores for multiple-bit transfers. This technique should only
be used when the hardware pitfalls are well-understood.
Netlisting Multiple Clock Designs
Each clock domain should have its own subsystem in a System Generator design. The
diagram below shows a two-domain design. The top-level block contains the Multiple
Subsystem Generator block and two subsystems which each comprise a clock domain.
Each subsystem has a System Generator block that sets the system clock period for that
clock domain.
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The diagram below illustrates the concept of putting domain-crossing blocks into their
own subsystem. When a multiple-domain design is netlisted, System Generator does the
following:
•
Creates an HDL file for Domain 0 (on the left), excluding the To FIFO block, and calls
the netlister to create a black-box netlist delivered as an NGC file;
•
Creates an HDL file for Domain 1 (on the right), excluding the From FIFO block, and
calls the netlister to create a black-box netlist delivered as an NGC file;
•
Invokes the Xilinx CORE Generator to produce a core for the FIFO block (middle);
•
Creates a top-level HDL wrapper that instantiates three block components.
Step-by-Step Example
This example shows how design hierarchy can be used to partition a System Generator
design into multiple asynchronous clock islands. The example also demonstrates how
Xilinx Shared Memory blocks may be used to communicate between these islands. Lastly,
the example describes how the Multiple Subsystem Generator block can be used to netlist
the complete multi-clock design.
1.
From the MATLAB window, change directory to the following:
<sysgen_tree>/examples/multiple_clocks/.
2.
Open the two_async_clks model from the MATLAB command window, and save it
into a temporary directory of your choosing.
Subsystem hierarchy is used in the example to partition the design into two synchronous
clock domains, to which you refer as domains A and B, that are internally synchronous to
a single clock, but asynchronous relative to each other. The design includes two
subsystems named ss_clk_domainA and ss_clk_domainB, which include logic
associated with clock domains, A and B, respectively. The blocks inside the
ss_clk_domainA subsystem operate in clock domain A while all blocks inside the
ss_clk_domainB subsystem operate in a second clock domain, B.
The asynchronous islands in the example communicate with one another via a shared
memory interface implemented using a pair of Xilinx Shared Memory blocks. The two
Shared Memory blocks are distributed so that one block resides in domain
ss_clk_domainA and the other resides in domain ss_clk_domainB. Both blocks
specify the same shared memory object name, bram_iface. This allows the Shared
Memory blocks to access a common address space during simulation. Note that in the
diagram there is no physical connection shown between the two shared memory halves.
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This is because the connection is implicitly defined by the fact that the two Shared Memory
blocks specify the same shared memory object name and therefore, share an address space.
When the two subsystems are wired together and translated into hardware, the shared
memory blocks are moved from their respective subsystems and merged into a block RAM
core. For more information on how this works, refer to the topic Multiple Subsystem
Generator.
The synchronous islands sample different input sources. Island ss_clk_domainA samples a
sinusoid input, while ss_clk_domainB samples a saw-tooth wave input. Each subsystem
writes its samples into opposite halves of the shared memory. Once an island has filled its
half of memory, it reads samples from the other island's half. You can simulate the design
to visualize of the model's behavior.
3.
Press the Simulink Start button to simulate the design.
4.
Open the scope to visualize the output signals.
Also shown in the output scope are the two clocks, clk_A and clk_B. At the default time
scale, it is difficult to distinguish the two. Zoom in to get a more detailed view.
Notice that clk_A and clk_B have different periods and are out of phase with one
another. Earlier, it was claimed that System Generator uses a single clock source per
design. In the scope, you clearly see two different clocks. How is this possible?
The answer is in the hierarchical construction of the design. All blocks are buried in at least
one level of hierarchy using subsystems. Because there is no System Generator block at the
top level, you can consider each subsystem as a completely separate System Generator
design (at least for the time being). In this model, you have effectively defined two clock
domains by giving the ss_clk_domainA and ss_clk_domainB subsystems different
Simulink system periods. This is allowed since you are treating these subsystems as
separate System Generator designs. The clock probes in the ss_clk_domainA and
ss_clk_domainB subsystems use the Simulink system periods in their respective
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subsystems to determine their output, hence different system periods yield different
system clocks.
Now consider the clocks defined by the System Generator block in the ss_clk_domainA
and ss_clk_domainB subsystems.
5.
Open the System Generator block parameter dialog boxes inside the
ss_clk_domainA and ss_clk_domainB subsystems.
The System Generator block dialog box in the ss_clk_domainA subsystem defines an
FPGA clock period of 10ns (i.e., a frequency of 100MHz). To simplify the sample period
values in the model, the 10 ns clock is normalized to a Simulink system period value of 2
sec. In the ss_clk_domainB subsystem, an FPGA clock period of 15ns (i.e., a frequency
66.7 MHz) is defined. Normalizing this clock period gives us a Simulink system period
value of 3 sec.
Because the two subsystems in this example implement multiple, synchronous, System
Generator domains, you will use the Multiple Subsystem Generator block to wire the
subsystems together into a single HDL top-level component that exposes two clock ports.
When the Multiple Subsystem Generator translates a design into hardware, it generates
each subsystem individually as an NGC netlist file. It also creates a top-level VHDL
component or Verilog module that instantiates the subsystem netlist files as black boxes,
and wires them together using shared memory cores as clock domain bridges.
You begin by using the Multiple Subsystem Generator block to netlist subsystems
ss_clk_domainA and ss_clk_domainB.
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6.
Open the Multiple Subsystem Generator dialog box by double clicking on the Multiple
Subsystem Generator block included in the top-level of the two_async_clks model.
7.
Pick a suitable target directory inside the Multiple Subsystem Generator dialog box.
The default directory is netlist.
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8.
Press the Generate button. You may leave the Part, Synthesis Tool, and Hardware
Description Language fields as they are.
Once the Multiple Subsystem Generator block is finished running, it will display a
message box indicating that generation is complete. It is worthwhile to take a look at the
generated results.
9.
cd into the design's target directory, netlist.
There are two NGC files in this directory: ss_clk_domaina_cw.ngc and
ss_clk_domainb_cw.ngc. These files store the netlist and constraints information
corresponding to the subsystems ss_clk_domaina and ss_clk_domainb. Note that
these NGC files include the clock wrapper layer logic associated with each subsystem. This
is necessary to ensure that any clock enable logic required by a multirate design is included
in netlist file. By using the clock wrapper layer of a design, the corresponding clock driver
components are automatically included in the netlist.
Also in this directory is a dual port memory core netlist file named
dual_port_block_memory_virtex2_6_1_ef64ec122427b7be.edn. This core
provides the hardware implementation for the Shared Memory blocks used in the original
design. The width and depth of the memory are based on values used in the Shared
Memory block configurations.
You will now take a look at the top-level HDL component that the Multiple Subsystem
Generator block produced for the design.
10. Open the two_async_clks.vhd file in a text editor.
This component defines the HDL top-level for the two_async_clks model.
entity two_async_clks is
port (
din_a: in std_logic_vector(7 downto 0);
din_b: in std_logic_vector(7 downto 0);
ss_clk_domaina_cw_ce: in std_logic := '1';
ss_clk_domaina_cw_clk: in std_logic;
ss_clk_domainb_cw_ce: in std_logic := '1';
ss_clk_domainb_cw_clk: in std_logic;
dout_a: out std_logic_vector(7 downto 0);
dout_b: out std_logic_vector(7 downto 0)
);
end two_async_clks;
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There are several interesting things to notice about the port interface. First, the component
exposes two clock ports (shown in bold text). The two clock ports are named after the
subsystems from which they are derived (e.g., ss_clk_domaina), and are wired to their
respective subsystem NGC netlist files. Also note that the top-level ports of each
subsystem (e.g., din_a and dout_a) appear as top-level ports in the port interface.
The Multiple Subsystem Generator block does not generate circuitry (e.g., a DCM) to
generate multiple clock sources. You may modify the top-level HDL component to include
the circuitry, or instantiate the top-level HDL as a component in a separate wrapper that
includes the clocking circuitry.
Creating a Top-Level Wrapper
If you decide to create a top-level HDL wrapper for your multi-clock System Generator
design, it should perform the following tasks at a minimum:
•
Instantiate the System Generator top-level component along with other wrapper logic
(e.g., a DCM);
•
Wire the System generator component to the other logic;
•
Create a new top-level port map which supersedes that from the System Generator
component.
The following is an example of making a top-level HDL component to instantiate clocking
circuitry. In this example, you take the output created when the example from the previous
topic is generated using the Multiple Subsystem Generator block. The resulting System
Generator design is called two_async_clks and the top-level HDL component is called
top_wrapper (for the case of VHDL synthesis).
Because the clock lines and main clock enables are inferred, the names of the clocks and
clock enables (with the _ce and _clk suffixes above) are generated automatically by
putting suffixes on the subsystem names from which the clocks are inferred. The other port
names, such as dout_a, are taken directly from the names given to the gateway blocks in
the System Generator design.
An example VHDL top-level wrapper to instantiate the entity two_async_clks, with
deletions made for clarity, is provided below. Note that the wrapper uses a DCM
component to generate the two clocks required by the System Generator design.
----------------------------------------------------------------------------- top_wrapper.vhd
-- Example Top Level Wrapper
--- This is an example top-level wrapper for instantiating a System
Generator
-- design along with a DCM. In this example, the DCM connects the two
clock
-- inputs of the System Generator block ('two_async_clks') to two
buffered
-- outputs of the DCM, namely, CLK0 and CLKFX. CLK0 is the same
frequency
-- and phase as the input clock, and CLKFX is configured to be twice the
-- frequency of the input clock.
-----------------------------------------------------------------------------library IEEE;
library unisim;
use IEEE.std_logic_1164.all;
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use unisim.vcomponents.all;
entity top_wrapper is
port (
clk : in std_logic;
din_a : in std_logic_vector(7 downto 0);
din_b : in std_logic_vector(7 downto 0);
dout_a : out std_logic_vector(7 downto 0);
dout_b : out std_logic_vector(7 downto 0)
);
end top_wrapper;
architecture structural of top_wrapper is
--------------------------------------- SysGen Model Component Declaration
-------------------------------------component two_async_clks
port (
din_a: in std_logic_vector(7 downto 0);
din_b: in std_logic_vector(7 downto 0);
ss_clk_domaina_cw_ce: in std_logic := '1';
ss_clk_domaina_cw_clk: in std_logic;
ss_clk_domainb_cw_ce: in std_logic := '1';
ss_clk_domainb_cw_clk: in std_logic;
dout_a: out std_logic_vector(7 downto 0);
dout_b: out std_logic_vector(7 downto 0)
);
end component;
component bufg
port(i: in std_logic;
o: out std_logic);
end component;
--------------------------------------- DCM Component Declaration
-------------------------------------component dcm
-- synopsys translate_off
generic (clkout_phase_shift : string := "fixed";
dll_frequency_mode : string := "low";
duty_cycle_correction : boolean := true;
clkdv_divide : real := 3;
clkfx_multiply : integer := 2;
clkfx_divide : integer := 1);
-- synopsys translate_on
port (clkin : in std_logic;
clkfb : in std_logic;
dssen : in std_logic;
psincdec : in std_logic;
psen : in std_logic;
psclk : in std_logic;
rst : in std_logic;
clk0 : out std_logic;
clk90 : out std_logic;
clk180 : out std_logic;
clk270 : out std_logic;
clk2x : out std_logic;
clk2x180 : out std_logic;
clkdv : out std_logic;
clkfx : out std_logic;
clkfx180 : out std_logic;
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locked : out std_logic;
psdone : out std_logic;
status : out std_ulogic_vector(7 downto 0));
end component;
--------------------------------------- DCM Attributes
-------------------------------------attribute dll_frequency_mode : string;
attribute duty_cycle_correction : string;
attribute startup_wait : string;
attribute clkdv_divide : string;
attribute clkfx_multiply : string;
attribute clkfx_divide : string;
attribute clkin_period : string;
attribute
attribute
attribute
attribute
attribute
attribute
attribute
signal
signal
signal
signal
signal
signal
signal
signal
signal
signal
duty_cycle_correction of dcm0 : label is "true";
startup_wait of dcm0 : label is "false";
dll_frequency_mode of dcm0 : label is "low";
clkdv_divide of dcm0 : label is "3";
clkfx_multiply of dcm0 : label is "2";
clkfx_divide of dcm0 : label is "1";
clkin_period of dcm0 : label is "10";
clk0unbuf : std_logic;
clk0buf : std_logic;
clkfxbuf : std_logic;
clk2xunbuf : std_logic;
clkfxunbuf : std_logic;
clkdvunbuf : std_logic;
clkdvbuf : std_logic;
ff1,ff2,ff3,ff4 : std_logic;
dcm_rst : std_logic;
intlock : std_logic;
------------------------------------------------------------------------------- The top level instantiates the SysGen design, a DCM, and two BUFGs.
-- The DCM generates two clocks of different frequencies.
-- These two clocks are used to drive the two different clock domains
-- in the SysGen block.
-----------------------------------------------------------------------------begin
dcm0: dcm
-- synopsys translate_off
generic map (dll_frequency_mode => frequency_mode,
clkdv_divide => clkdv_divide_generic,
clkfx_multiply => clkfx_multiply_generic,
clkfx_divide => clkfx_divide_generic)
-- synopsys translate_on
port map (clkin => clk,
clkfb => clk0buf,
dssen => '0',
psincdec => '0',
psen => '0',
psclk => '0',
rst => dcm_rst,
clk0 => clk0unbuf,
clk2x => clk2xunbuf,
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clkfx => clkfxunbuf,
clkdv => clkdvunbuf,
locked => intlock);
bufg_clk0: bufg
port map (i => clk0unbuf,
o => clk0buf);
bufg_clkfx: bufg
port map (i => clkfxunbuf,
o => clkfxbuf);
--------------------------------------------------------------------- This is the DCM reset. It is a four-cycle shift register used to
-- hold the DCM in reset for a few cycles after programming.
-------------------------------------------------------------------flop1: FDS port map (D => '0', C => clk, Q => ff1, S => '0');
flop2: FD port map (D => ff1, C => clk, Q => ff2);
flop3: FD port map (D => ff2, C => clk, Q => ff3);
flop4: FD port map (D => ff3, C => clk, Q => ff4);
dcm_rst <= ff2 or ff3 or ff4;
------------------------------------------------------------- SysGen Component Port Mapping
-- One clock input is being connected to clk0 of the DCM,
-- and the other clock is being connected to clkfx.
-----------------------------------------------------------two_async_clks: two_async_clks
port map (
din_a => din_a,
din_b => din_b,
ss_clk_domaina_cw_ce => '1',
ss_clk_domaina_cw_clk => clk0buf,
ss_clk_domainb_cw_ce => '1',
ss_clk_domainb_cw_clk => clkfxbuf,
dout_b => dout_b);
end structural;
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Using ChipScope Pro Analyzer for Real-Time Hardware Debugging
This tutorial demonstrates how to connect and use the Xilinx Debug Tool called ChipScope
Pro within Xilinx System Generator. The integration of ChipScope Pro in the System
Generator flow allows real-time debugging at system speed. By inserting a ChipScope
block into your System generator design, you can debug and verify all the internal signals
and nodes within your FPGA. After reviewing some characteristics of the ChipScope Pro
Debug tool, this tutorial walks you through the steps of adding the ChipScope block to a
simple Simulink model, running it on a hardware platform and probing internal signals.
The following topics are discussed:
•
ChipScope Pro Overview
•
ChipScope within System Generator
•
Real-Time Debug with the ChipScope Pro Analyzer
•
Importing data back into MATLAB workspace from ChipScope
Software Requirements: Refer to the topic Software Prerequisites.
Hardware Requirements: Any hardware demo board that has a JTAG port (the
XtremeDSP Development kit is used in this tutorial).
ChipScope Pro Overview
The increasing density of FPGA devices has rendered attaching test probes to these devices
impractical. The ChipScope™ Pro tools integrate key logic analyzer hardware components
with the target design inside Xilinx Virtex™, Virtex-E, Virtex-II, Virtex-II Pro™, Spartan™II, Spartan-IIE and Spartan-3 devices. The ChipScope Pro tools communicate with these
components during system operation and in effect provide the designer with a logic
analyzer for nodes inside the Xilinx FPGA. ChipScope gives you a deep trace memory, fast
clock speeds and multiple trigger options, which can vary in complexity. You can easily
capture and view signal activity inside your FPGA without having to dedicate critical logic
space, come up with complex capture schemes, or allocate additional I/O pins. Data
samples are captured based on user-defined trigger conditions and stored in internal block
memory. All control and data transfer is done via the JTAG port eliminating the need to
drive data off-chip using I/O pins.
Please refer to the following Web page for further details on ChipScope Pro:
http://www.xilinx.com/ise/optional_prod/cspro.htm
ChipScope in System Generator
This example shows how to modify a Simulink model to integrate the ChipScope block
and to select the data to be captured and viewed for debugging. The steps are as follows:
1.
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From the MATLAB console, change the directory to
<sysgen_tree>/examples/chipscope. The following files are located in this
directory:
♦
chip.mdl – Your working model.
♦
chip_soln.mdl – Solution model, including the ChipScope block.
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♦
osc_clock_2v80.bit – Bitstream to program the XC2V80 device on the
XtremeDSP development kit. This device is used for clock management and is
required for proper operation.
2.
Open chip.mdl model from the MATLAB console. This model represents a simple
sine/cosine table driven by an 8-bit counter. Both sine and cosine functions have been
selected, enabling you to probe, and later plot both waveforms.
3.
The 8-bit counter counts modulo 255. It is to be used to trigger ChipScope. The most
significant bit is extracted with a slice block and drives an LED on the XtremeDSP
board.
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4.
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Simulate the model by clicking on the Start simulation Icon
At this point, without
modifying the model, you should be able to see the following plot.
♦
The first plot represents the most significant bit of the 8-bit counter. The MSB
becomes 1 when the counter output is within the range of 128 through 255.
♦
The second plot represents the full output of the counter.
♦
The third plot shows the sine. If you zoom in at the beginning of time, you will
notice a 2 clock-cycle delay due to the pipelining implemented in the SineCosine
table.
♦
The fourth output represents the cosine. This output has the same 2 clock-cycle
delay as the Sine Wave.
5.
Integrate ChipScope in the Simulink model. The ChipScope block can be found in the
Simulink Library Browser in the Xilinx Blockset, under the Tools library. While
holding down the left mouse button, select the ChipScope block and drag it into the
open chip Simulink model.
6.
Double click on the ChipScope block in order to set the following parameters:
♦
Number of trigger ports: Multiple trigger ports allow a larger range of events to
be detected and can reduce the number of values that must be stored. Up to 16
trigger ports can be selected. In this example, only one is used.
♦
Display settings for trigger port: For each trigger port, the number of match units
and the match type need to be set. The pulldown menu displays options for a
particular trigger port. For N ports, the display options for trigger port 0 to N-1
can be shown. In this example, there is one Trigger port named Trig0. This option
should therefore be set to 0.
♦
Number of match units: Using multiple match units per trigger port increases the
flexibility of event detection. One to four match units can be used in conjunction
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to test for a trigger event. In this example, this option should be set to 1 since you
are only checking for one condition (i.e., the 8-bit counter value). You will set the
trigger value at run-time in the ChipScope Pro Analyzer.
♦
Match type: This option can be set to one of the following six types:
1. Basic: performs = or <> comparisons
2. Basic With Edges: in addition to the basic operations high/low, low/high
transitions can also be detected
3. Extended: performs =, <>,>,<, <=, >= comparisons
4. Extended With Edges: in addition to the extended operations, high/low,
low/high transitions can also be detected.
5. Range: performs =, <>, >, >=, <, <=, in range, not in range comparisons
6. Range With Edges: in addition to the range operations, high/low, low/high
transitions can also be detected.
In this example, set the Match Type to Basic with Edges
♦
Number of data ports: Up to 256 bits can be captured per sample. This means that
the sum over all ports of the bits used per port must be less than or equal to 256.
System Generator propagates the data width automatically; therefore, only the
number of data ports needs to be specified. In this example, you want to view the
sine and cosine, hence you enter 2.
♦
Depth of capture buffer: The depth of the capture buffer is a power of 2, up to
16384 samples for Virtex-II, Virtex-II Pro, and Spartan-3 device families, and 4096
for Virtex, Virtex-E, Spartan-II and Spartan-IIE device families. In this example,
set the depth to 512.
After parameterization the ChipScope GUI should look like the following:
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7.
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Connecting the ChipScope Block
The signal used to trigger ChipScope is the counter output. The two buses that you
want to probe are the sine and cosine from the Sine/Cosine table. Connect the signals
appropriately as shown on the following figure:
Note that the names of the ports on the ChipScope block are specified by names given
to the signals connected to the block, e.g. Sin and Cos.
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8.
Location Constraints
Now that the design is fully implemented and simulates correctly, the next step is to
prepare it for connection to our hardware target. Although it can work on any
hardware platform, the process is described for the XtremeDSP Development kit.
Two pins need to be locked down in this design: The LED and the clock pin.
♦
LED Pin: Double click on the Gateway Out1 block, select Specify IOB Location
constraint and type in {'Y11'} (note the need for single quotes).
♦
Clock Pin: Double click on the System Generator block, set the clock period to
25ns and the clock pin location to Y13
If you are using a different board, pin location should be modified appropriately.
9.
System Generator GUI settings
The last two parameters that should be updated before generating a bitstream are the
target device and the compilation target.
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Double click on the System Generator token and select the part Virtex2 xc2v20004fg676 or xc2v3000-4fg676 depending on which part you have on your board.
♦
Set the Compilation target to Bitstream.
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♦
Double check that your System Generator parameters match the ones shown on
the following screen shot:
10. Bitstream Generation
Xilinx System Generator software automatically calls both the Core Generator and
ChipScope generator to create the netlist and cores. In addition, when the Bitstream
target is selected, a configuration bitstream is created.
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♦
Create a bitstream by pressing the Generate button on the System Generator GUI.
♦
The Core Generator is automatically called to generate the Sine/Cosine table and
Counter netlists. ChipScope Generator is called to create an Integrated Logic
Analyzer (ILA) core and an ICON core to communicate with the ChipScope Pro
software via the JTAG port.
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Using ChipScope Pro Analyzer for Real-Time Hardware Debugging
Real-Time Debug
The next step is to run the design on the XtremeDSP development kit and view the probed
outputs with the ChipScope Pro Analyzer.
1.
Connect Parallel Cable IV to the General JTAG (J13) header of the XtremeDSP
development kit. The VCC pin is the pin closest to the top edge of the board, furthest
away from the PCI connector. It is also necessary to connect it to the USB port for
power up.
2.
Open Fuse to power up the board
With the XtremeDSP kit, it is first necessary to power up the board with the FUSE
software.
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Select Start > Programs > FUSE > Software > FUSE Probe
♦
From FUSE, select Card Control > Open Card. Then select USB for the interface
and click on Locate Card. At this point it should find the BenOne card and you
should see the following on the top left corner of your FUSE window.
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If you have any issues with this procedure, please refer to the XtremeDSP
Development Kit User's Guide.
3.
Open ChipScope Pro Analyzer (Refer to the topic Software Prerequisites for details on
the version to use)
♦
Open JTAG Chain by clicking on the following Icon , or by clicking on JTAG
Chain > Xilinx Parallel Cable and selecting Xilinx Parallel IV Cable.
Note the index for the Virtex-II devices available on the XtremeDSP kit: xc2v2000 or
xc2v3000 is index 3, and xc2v80 is index 4.
4.
5.
Configure the FPGAs
♦
Under the New Project Window, right click on Device 3 and select Configure >
Device 3. At this point, you need to look for the bitstream which was generated in
step 10 of the previous topic. Select New File and scroll to your project directory:
<sysgen_tree>/examples/chipscope/netlist/chip_cw.bit. After
configuration, the status window at the bottom of the ChipScope Analyzer should
reflect that one ChipScope core was found in the JTAG chain.
♦
Similarly, select Device 4 and Configure it with the osc_clock_2v80.bit file
provided in the ChipScope project directory. This second bitstream is used to
program the clock driver FPGA on the board.
Import ChipScope Project File
System generator creates a project file for ChipScope in order to group data signals into
buses. A bus is created for each data port so that it can be viewed in the same manner
(sign and precision) in which it was viewed in the Simulink environment.
Load this project file by going under File > Import > Select New File, and select
<sysgen_tree>/examples/chipscope/netlist/temp/chip_chipscope.cd
c.
6.
Plot the Sine Waves
In the New Project window, under Device 3 > Unit 0 ILA, double click on Bus Plot.
A Bus Plot window appears. Select Cos and Sin in the Bus Selection section, and then
arm the trigger by hitting the
button. Since you have not yet set any trigger
conditions, values are captured immediately. Both the sine and cosine appear as
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shown below. You can change the display option to represent the waveforms with
points, lines, or both.
7.
Setup Trigger
In the Trigger Setup window, change the current XXXX-XXXX value with all 00000000. Once the counter hits 0, ChipScope starts capturing values. Earlier, you setup the
buffer to 512, so 512 data points can be visualized in ChipScope.
Re-capture the data by hitting then
button.
Again, you see a 2 clock delay at the beginning of time on the sine wave due to the 2
clock latency through the SineCos Look Up Table. Modify the trigger value to 00000010 (decimal 2) and re-capture the data. Now the sine and cosine start respectively at
0 and 1.
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Importing Data Into MATLAB Workspace From ChipScope
Now you can export the data captured by ChipScope back into the MATLAB workspace.
1.
Export data from ChipScope Pro Analyzer
♦
2.
Start MATLAB and change the current working directory to the location where you
saved sinecos.prn.
♦
3.
Type xlLoadChipScopeData('sinecos.prn'); This loads the data from the
.prn file into the MATLAB workspace. In the workspace there are two new arrays
named Sin and Cos.
You can plot the values using the MATLAB plot function.
♦
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Select File > Export option from within ChipScope Pro Analyzer. Select ASCII
format and choose Bus Plot Buses to export. Press the Export button and save the
file as sinecos.prn.
Type: plot(1:512, Sin, 1:512, Cos) and the following plot is generated:
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Chapter 2
Hardware/Software Co-Design
The Chapter covers topics regarding developing software and hardware in System
Generator.
Hardware/Software Co-Design
in System Generator
A collection of tutorials that touch on designs with
embedded processors.
Integrating a Processor with
Custom Logic
A collection of tutorials that touch on designs with
embedded processors
EDK Support
Documentation of support for the Xilinx Embedded
Development Kit.
Designing with Embedded
Processors and Microcontrollers
A collection of tutorials that touch on designs with
embedded processors.
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Hardware/Software Co-Design in System Generator
System Generator provides three ways for processors to be brought into a model;
processors can be imported through a Black Box block, a PicoBlaze Microcontroller block
and an EDK Processor block.
Black Box Block
The Black Box approach provides the largest degree of flexibility, at the cost of design
complexity. You can interface any processor HDL into a System Generator design in this
manner. All ports and buses on the processor can be exposed to the System Generator
diagram, and you are free to engineer the required connectivity between the processor and
other System Generator blocks. You also have complete control over software compilation
issues. Please refer to the topic Importing HDL Modules for more information.
PicoBlaze Block
The PicoBlaze block provides the smallest degree of flexibility but is the least complex to
use. The Xilinx PicoBlaze Microcontroller block implements an embedded 8-bit
microcontroller using the PicoBlaze macro, and exposes a fixed interface to System
Generator. Ordinarily, a single block ROM containing 1024 or fewer 8 bit words serves as
the program store. You can program the PicoBlaze using the PicoBlaze Assembler
language. This flow is documented in the topic Designing PicoBlaze Microcontroller
Applications.
EDK Processor Block
The EDK Processor block provides an interface to MicroBlaze processors created using the
Xilinx Platform Studio (XPS). The EDK Processor block allows System Generator Shared
Memory blocks (i.e., "From/To Register"s, "From/To FIFOs", and "Shared Memory"
blocks) to be associated with a processor through an automatically generated memory map
interface. Once associated, that memory can be read or written in software running on the
MicroBlaze processor. This flow is documented in the topic Integrating a Processor with
Custom Logic.
The EDK Processor block can import a MicroBlaze specified through an EDK project
created using Xilinx Platform Studio and Base System Builder. Alternatively, a System
Generator design with an EDK Processor block can also be exported into an EDK project.
The export process creates a PLB-based or FSL-based pcore, which can be added to any
XPS project and communicate with the MicroBlaze or PowerPC processor.
Integrating a Processor with Custom Logic
Integrating a processor with a piece of user-defined logic is typically a fairly involved
process. The communications between a processor and a custom piece of hardware often
occurs over a shared bus. Additionally, the information conveyed frequently consists of
different types of data; for example data for processing, data denoting the status of the
hardware or data affecting the mode of operation. Organizing how this data is transferred
between the processor and custom logic is a tedious and error prone process that would
benefit from automation. Furthermore, connectivity is only half of the problem, writing
software to communicate with custom logic can also be challenging.
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The EDK Processor block provides a solution to both these problems through automation.
The EDK Processor block encourages the interface between the processor and the custom
logic to be specified via shared-memories. Shared-memories are used to provide storage
locations that can be referenced by name. This allows a memory map and the associated
software drivers to be generated.
Please refer to the EDK Processor block documentation for information on the use of the
block. The topics that follow describe the memory map and software features of the drivers
that are generated.
Memory Map Creation
Explains the memory map generated when
shared memories are added to a processor.
Hardware Generation
Documents the different hardware generation
options.
Hardware Co-Simulation
Explains how to create a hardware cosimulation model for the EDK Processor block.
Generating Software Drivers
Documents how software drivers are created.
Writing Software for EDK
Processors
Documents the process of writing software to
control hardware created in System Generator.
Asynchronous Support for EDK
Processors
Documents the capability in System Generator,
in both import and export mode, to allow the
processor and the System Generator design to
run with different clocks.
Memory Map Creation
A System Generator model is shown on the bottom-right of the figure above. The System
Generator model corresponds to custom logic that will be integrated with the MicroBlaze
processor. In the construction of the model, shared-memories are used in locations where
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software access is required. For instance, the status of the hardware might be kept in a
register. To make that status information visible in the processor, the register is replaced by
a named shared-register. Naming the shared-register "status" gives the name of the
memory context that will be useful later on during software development.
The block GUI of the EDK Processor block allows these shared-memories to be added to
the memory map of the processor (bottom-left of the figure). The block diagram at the top
of the figure above shows the flow of data. When a shared memory is added to the memory
map of the processor, the EDK Processor block creates the corresponding matching shared
memory. This shared memory is attached to the memory map that is generated for that
EDK Processor block. Next, a bus adaptor is used to connect that memory map to the
MicroBlaze processor.
When hardware is generated, each shared memory pair is implemented with a single
physical memory. The implementation for each class of shared memory is documented in
the topic Shared Memory Support, found under the topic Using Hardware Co-Simulation.
Hardware Generation
The EDK Processor block supports two modes of operation: EDK pcore generation and
HDL netlisting. The different modes of operation are illustrated below and can be chosen
from a list-box in the EDK Processor block's GUI.
EDK pcore Generation Mode
The Xilinx Embedded Development Kit (EDK) allows peripherals to be attached to
processors created within the EDK. These peripherals can be packaged as pcores. Each
pcore contains a collection of files describing the peripheral's hardware description,
software drivers, bus connectivity and documentation.
When set in EDK-pcore-generation mode and used with the EDK Export Tool (selected via
the System Generator block), System Generator is able to create a pcore from the given
System Generator model. The figure above shows the part of the model that is created as a
pcore. When set in this mode, the assumption is that the MicroBlaze added to the model is
just a place-holder. Its actual implementation will be filled in by the EDK when the
peripheral is finally added into an EDK project. As such, the pcore that is created consists
of the custom logic, the generated memory map and virtual connections to the custom
logic, and the bus adaptor.
HDL Netlist Mode
An EDK processor can also be brought into a System Generator model when HDL
netlisting mode is selected. The EDK Processor block can be set to HDL netlisting mode
only when an EDK project is supplied to the block. When in HDL netlisting mode, the
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processor described in the EDK project will be imported into System Generator as a black
box. The supplied EDK project is also augmented with the bus interfaces necessary to
connect the System Generator memory map to the processor. During netlisting, the
MicroBlaze and the generated memory-map hardware are both netlisted into hardware.
This mode can be used for software-based simulation of the processor, or hardware cosimulation.
Hardware Co-Simulation
Currently the EDK Processor block provides hardware-based simulation through
hardware co-simulation. Creation of a hardware co-simulation block follows the standard
co-simulation flow described in the topic Using Hardware Co-Simulation.
You may use the EDK's XPS tool to write and compile your software. However before
simulation can begin, the Compile and update bitstream button in the co-simulation
block's Software tab must be used to put the compiled C-code into the bitstream.
When used in conjunction with a hardware-board supported by network-based hardware
co-simulation, it is possible to free up the JTAG port on the FPGA and use that for software
debug with XMD.
Generating Software Drivers
In both modes of operation, the software driver templates are automatically created when
a memory map is generated. The driver templates are only elaborated during the
compilation of software libraries by the EDK. This can be accomplished from the EDK.
Once the software libraries have been compiled, the drivers can be referenced and the
software documentation can also be accessed.
When the EDK Processor block is placed in EDK pcore generation mode, the elaboration of
the software drivers depend on the instance name of the pcore. For example, a pcore
created from System Generator may be called sysgen_fft_sm. This is the name of the
peripheral. Since more than one of these peripherals can be added to an EDK processor,
each instance of the peripheral needs a unique name. The EDK automatically assigns a
numeric postfix to a peripheral's name. So when the peripheral is first added, it might be
called sysgen_fft_sm_0, this is the instance name of the peripheral. You can change the
instance name of a peripheral. Please refer to the EDK XPS documentation for further
information.
When the EDK Processor block is placed in HDL netlisting mode and an EDK Project is
imported into the System Generator model, System Generator automatically places a
special peripheral into the EDK project. The peripheral provides the connectivity between
the MicroBlaze and the System Generator model. This peripheral is given the instance
name xlsg_iface. Only one instance of this peripheral is allowed; an EDK Project can only be
associated with one EDK Processor block.
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Writing Software for EDK Processors
Software drivers and documentation for a peripheral is elaborated after all software
libraries have been compiled in the EDK. After compilation, the software documentation
can be accessed from the EDK.
The figure above shows a screen capture of the EDK XPS tool. Locate the System Generator
peripheral from the System Assembly view and right click for a pop-up menu. Select
View API Documentation to bring up the documentation. If this option is not available,
the drivers need to be compiled. This can be done in XPS by selecting the menu option
Software > Generate Libraries and BSPs.
Please refer to the generated documentation for header file information, driver calls,
memory maps and also example code.
The generated software drivers contain four basic functions for accessing sharedmemories. In the table below, <inst> refers to the instance name given to the peripheral.
int <inst>_Read (unsigned int memName,
unsigned int addr,
unsigned int* val);
int <inst>_ArrayRead (unsigned int memName,
unsigned int startAddr,
unsigned int transferLength,
unsigned int** valBuf);
int <inst>_Write (unsigned int memName,
unsigned int addr,
unsigned int val);
int <inst>_ArrayWrite (unsigned int memName,
unsigned int startAddr,
unsigned int transferLength,
const unsigned int* valBuf);
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Asynchronous Support for EDK Processors
Asynchronous support for processors allow for the processor and the accelerator hardware
hanging off the processor to be clocked with different clocks. This allows the hardware
accelerator to run at the fastest possible clock rate, or at a clock rate that is necessary for its
correct functioning, for example when it is required to interface with an external
peripheral.
This feature is enabled when the Dual Clock check box is selected in the EDK Processor
block GUI's Implementation tab. The figure below shows how clocks will be connected for
the import and export flow, in the export flow, the MicroBlaze (MB) block is not present.
Basically, the custom logic design in System Generator is driven with the clk clock and the
processor system is driven with the xps_clk clock. The clock source that drives the PLB bus
in the MicroBlaze processor system is extracted to drive the bus adaptor, the memory map,
and halves of the shared memories.Shared memories straddle between these two domains
(e.g. the clk domain and the plb_clock domain) and are driven by both these clocks. Shared
Registers are not supported in this flow. In the import flow where an XPS project is
imported into System Generator, the PLB bus on the processor must be driven with the
same clock as the xps_clk signal.
When Dual Clock is enabled and a design is netlisted for Hardware Co-simulation, a
slightly different clock wiring topology is used. This is shown in the figure below. The
clock source from the board is bifurcated with one branch going into the Hardware Cosimulation module before being connected to the clk clock (depicted in the figure above).
The other branch is routed through a clock buffer and connected to the xps_clk clock
signal.
This topology allows for the custom logic designed in System Generator to be singlestepped, while allowing the MicroBlaze to continue in free-running mode. This allows for
clock-sensitive peripherals (such as the RS232 UARTS) to work when the Hardware CoSimulation token is set to single-step.
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In Hardware Co-simulation, the processor subsystem is driven by the board clock directly.
This means that the processor subsystem must be able to meet the requirements set by this
clock. In hardware co-simulation, it is possible for users to select different ratios of clock
frequencies based of the input board frequency. Note that this hardware co-simulation
clock is generated in the hardware co-simulation module and is not available to the
processor subsystem.
For exmaple, if the input board frequency is 125MHz, and the hardware co-simulation
frequency is set to 33 Mhz, only the custom logic portion of the design will be constrained
to 33 MHz, the MicroBlaze must still run at 125 MHz. If the MicroBlaze cannot meet timing
at this speed, the user needs to instance a clock generator pheripheral in their XPS project
and slow down the clock in that way.
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EDK Support
EDK Support
Importing an EDK Processor
How to import an EDK project into System
Generator using the EDK Import Wizard.
Exposing Processor Ports to
System Generator
How to route top-level ports in the EDK into
System Generator.
Exporting a pcore
How to export a System Generator design to the
EDK as a pcore.
Importing an EDK Processor
A processor created using the Xilinx Platform Studio (XPS) tool, found in the Xilinx EDK
suite of tools, can be imported into a System Generator model using the EDK Import
Wizard.
There are two ways to launch the EDK Import Wizard in the EDK Processor block: (1) press
the Import… button, or (2) select HDL netlisting when the EDK project field is empty.
Note: When you import the EDK Project into System Generator, there are modifications made to the
EDK project. These modifications are described in the following topic.
EDK Import Wizard
When the Wizard starts up, it prompts you for an EDK project file (xmp file).
Clicking the Import... button starts the import process.
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Note: The import process will alter your EDK project to work inside System Generator. If you wish
to retain an unadulterated version, please make a copy before importing. System Generator
automatically backs up the hardware platform specification (i.e., the MHS file) and the software
platform specification (the MSS file) of the EDK project to files with the "bak" suffix.
When an EDK project is imported into System Generator, the EDK project is augmented
with a pair of FSL, or a PLB46 interface depending on the options made on the EDK
Processor block. A pcore (xlsg_iface for FSL and xlsg_plbiface for PLB) is also added to
provide software drivers for the interface.The MHS and MSS files in the EDK project will
be altered. Following that, the HDL files that describe the processor will be generated and
linked to your System Generator project.
Making Changes to Processor Hardware After an Import
After importing an EDK project, further changes to the hardware inside of the EDK will
not be reflected inside of System Generator. In other words, the hardware makeup of the
processor is now fixed. If changes to the processor hardware are to be made, the EDK
project must be re-imported using the EDK Import Wizard.
It is recommended that you re-import an EDK project when it is changed. The EDK
Processor block can detect the PLB or FSL interfaces and the related pcores that are
automatically added by System Generator during a previoius import, and will not include
redundant hardware or software to the XPS project.
Limitations
Currently the Wizard can only import single processor projects. Only the MicroBlaze
processor is supported. Peripherals added to the processor cannot conflict with the
resources used by other System Generator services. For instance, if network-based
hardware co-simulation is used, the EDK project cannot make use of the peripherals using
the Ethernet MAC.
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EDK Support
Exposing Processor Ports to System Generator
The preferred mechanism for getting data to and from the processor and System Generator
is via shared-memories. It is however possible to expose ports on the top-level of the
processor to System Generator.
The top-right box in the figure above shows a snippet from an EDK project in XPS. The
external port list has among other ports, a user-defined port called myExternalPort.
After importing the EDK project, open up the processor's block GUI in System Generator.
Select the Advanced tab to reveal the processor port interface table.
The port list shows all the top-level ports available on the processor. This port list has been
filtered to remove clock ports and also signals used by System Generator to implement the
memory-map interface. In this example, the RS232 ports, sys_rst_pin and myexternalport are
shown to be ports that can be exposed to the top-level of the System Generator block.
Selecting the expose check box will cause the port to be exposed on the EDK Processor
block. As shown in the figure above, the display name of the port can be changed, should
the original name be too long.
This mechanism allows ports from the processor to be directly exposed to the System
Generator design without going through the memory map generated by System
Generator. You may choose to do this to expose the reset ports on the processor, or to
expose interrupt ports directly to the System Generator diagram.
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Exporting a pcore
System Generator designs containing an EDK Processor block can be exported as an EDK
pcore using the EDK Export Tool compilation target on the System Generator block.
Before exporting to the EDK as a pcore, the EDK Processor block must be configured for
"EDK pcore generation". This can be done by opening the EDK Processor block GUI and
selecting the relevant drop down option in the "Configure processor for" parameter.
Please refer to the topic EDK Export Tool for more information.
Designing with Embedded Processors and Microcontrollers
Designing PicoBlaze Microcontroller Applications
The PicoBlaze block in System Generator implements an 8-bit microcontroller.
Applications requiring a complex, but non-time critical state machine as well as data
processing applications are candidates to employ this block. The microcontroller is fully
embedded into the device and requires no external support. Any additional logic can be
connected to the microcontroller inside the device providing ultimate flexibility.
PicoBlaze Overview
The following example uses PicoBlaze 3 (hereto referred to simply as PicoBlaze), which is
optimized for low resource requirements. A memory block is used as a program store for
up to 1024 instructions.
Signal
148
Direction
Description
in_port[7:0]
Input
Input Data Port. During an
INPUT operation, data is
transferred from the port to a
register.
brk
Input
Interrupt. Must be at least two
clock cycles in duration.
rst
Input
Reset
instr[17:0]
Input
Instruction Input.
out_port[7:0]
Output
Output Data Port.
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Signal
Direction
Description
port_id[7:0]
Output
Port Address.
rs
Output
Read Strobe.
ws
Output
Write Strobe.
addr[9:0]
Output
Address of the next instruction.
ack
Output
Interrupt Acknowledge.
Architecture Highlights
•
43 - 66 MIPS (dependent upon device type and speed grade)
•
Fast interrupt response
•
96 slices, 0.5 to 1 block RAM
•
16 8-bit general-purpose registers
•
64-byte internal RAM
•
Internal 31-location CALL/RETURN stack
•
256 input and 256 output ports
1Kx18
Instruction
PROM
31x10
CALL/RETURN
Stack
Predictable performance, two clock cycles per instruction
Program Counter
(PC)
•
PORT_ID
64-Byte
Scratchpad RAM
OUT_PORT
Flags
Instruction
Decoder
Constants
INTERRUPT
16 Byte-Wide Registers
IE Enable
s0
s4
s8
sC
IN_PORT
s1
s5
s9
sD
s2
s6
sA
sE
s3
s7
sB
sF
Z Zero
C Carry
Operand 1 ALU
Operand 2
PicoBlaze Instruction Set Architecture
PicoBlaze is a hardware-centric microcontroller, which can be programmed using
assembly code. It supports a program length up to 1024 instructions. Requirements for
larger program space are typically addressed by using multiple microcontrollers.
16 General Purpose Registers
There are 16 8-bit general-purpose registers specified 's0' to 'sF'.
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ALU
The Arithmetic Logic Unit (ALU) provides operations such as add, sub, load, and, or, xor,
shift, rotate, compare, and test. The first operand to each instruction is a register to which
the result is stored. Operations requiring a second operand can specify either a second
register or an 8-bit constant value.
Flags and Program Control
The result of an ALU operation determines the status of the zero and carry flags. The zero
flag is set whenever the result is zero. The carry flag is set when there is an overflow from
an arithmetic operation. The status of the flags can be used to determine the execution
sequence of the program using conditional program flow control instructions such as
jump and call.
Input/Output
There are 256 input ports and 256 output ports. The port being accessed is indicated by an
8-bit address value provided on port_id. The port address can be specified in the
program as an absolute value or indirectly specified as the contents of a register. During an
input operation, the value provided to in_port is transferred into any of the 16 registers.
During an output operation, a value is transferred from a register to out_port.
Interrupt
The processor provides a single interrupt input port, brk. When interrupts are enabled,
setting brk to 1 causes the program counter to be set to memory location 0x3FF, where a
jump vector to the interrupt service routine is stored. At this time, a pulse is generated on
the ack port (two clock cycles after brk is asserted), the control flags are preserved and
further interrupts are disabled. The return instruction ensures that the end of an interrupt
routine restores the status of the control flags and specifies if future interrupts should be
enabled.
For extensive details regarding the feature and instruction set, please refer online to the
topic PicoBlaze User Resources.
Tutorial Example - Using PicoBlaze in System Generator
In the following example, you modify a PicoBlaze program that alters the output
frequency of a Direct Digital Synthesizer (DDS) during an interrupt.
A Simulink model and PicoBlaze assembler code are provided but need modification.
1.
From the MATLAB console, change directory to
<sysgen_tree>/examples/picoblaze. The following files are located in this
directory:
♦
Pico_dds.mdl – An unfinished Simulink model
♦
Pico_code.psm – Unfinished PicoBlaze code
2.
Open Pico_dds.mdl.
3.
Modify the design.
a.
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Find the PicoBlaze block in the Xilinx Blockset Library under Index or Control
Logic and add it to the model where indicated. The default settings of the block do
not give the same number of ports as is expected by the model. This will be
corrected in the following step. You may need to resize the block to fit into the
space allocated in the design.
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b. Double-click the block and set Version to PicoBlaze 3. Turn off the option to
Display internal state. Connect the ports to the existing lines in the model.
c.
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to the model where indicated. Make sure it is connected properly, as shown in the
figure below:
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d. Double-click the PicoBlaze Instruction Display block and set the Version to
PicoBlaze 3. Check the Disable Display option. Disabling the display option
allows the simulation to run without the overhead of updating the block display.
4.
e.
Find the ROM block in the Memory Library and add it to the model where
indicated. Flip the block by Right clicking on the block and selecting Format > Flip
Block. Attach the ports to the existing lines.
f.
Change the Single-Step Simulation block to be in continuous mode by double
clicking on the block.
Configure the program store. Double click the ROM to do the following.
With the Basic tab selected:
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a.
The ROM block is used to store the PicoBlaze instructions. The depth of the ROM
must be set to 1024. This is because the program uses interrupts and setting brk to
1 causes the program counter to be set to 0x3FF.
b.
As detailed in step 5, the code is assembled and produces an initialization file for
the memory named fill_pico_code_program_store.m. Hence the ROM
Initial Value Vector should be set to fill_pico_code_program_store.
c.
To increase the performance for synchronous designs, the Latency should be set to
1.
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Click on the Output tab and enter the following:
a.
5.
The Word Type should be Unsigned and Number of Bits should be set to 18 with
the Binary Point at 0.
Edit the PicoBlaze assembly program.
a.
Open pico_code.psm.
b. Add instructions as described in the pico_code.psm file. For detailed
information about the PicoBlaze instruction set see the Xilinx Application Note
XAPP627 at http://www.xilinx.com/bvdocs/appnotes/xapp627.pdf
c.
6.
Save the file.
Run the assembler to generate the memory initialization file.
In the MATLAB command window, type:
>> xlpb_as -p pico_code.psm
xlpb_as stands for Xilinx PicoBlaze Assembler.
A file named fill_pico_code_program_store.m was created.
7.
Simulate the Simulink model.
Run the simulation by clicking on the Start Simulation Icon.
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Output should look like this:
Notice the sine wave frequency increasing proportionally to the phase increment.
8.
Utilize Debug Tools
If the program is not working properly, there are several tools that can be utilized to ease
debugging. Deselecting the Disable Display checkbox in the PicoBlaze Instruction
Display block causes the block to be activated, displaying the updated program counter
and instruction each clock cycle. In conjunction with enabling the display, the registers and
control flag values can be viewed by selecting the Display Internal State in the PicoBlaze
Microcontroller block. Change the Single-Step Simulation block to single-step mode by
double clicking on the block. Step through the simulation to debug.
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Designing and Exporting MicroBlaze Processor Peripherals
The Xilinx Platform Studio (XPS) tool suite allows the development of customized
MicroBlaze and PowerPC processor systems. A hardware peripheral of the processor
system is called “pcore”, which consists of a bundle of design files organized according to
a specific structure. These design files describe the hardware implementation, the
connection interface, and software drivers of the XPS pcore.
The EDK Processor block in conjunction with the EDK Export Tool allows customized
processor hardware peripherals to be designed in System Generator. A System Generator
design can be exported as an XPS pcore, which can be included and used in an XPS project.
The following tutorial illustrates the creation of a XPS pcore using System Generator.The
files used in this tutorial can be found in: <sysgen_tree>\examples\EDK\rgb2gray,
where <sysgen_tree> denotes the System Generator installation directory.
Tutorial Example - Creating MicroBlaze Peripherals in System Generator
Note: You must have EDK installed to complete this tutorial.
1.
Open the rgb2gray model from pathname
<sysgen_tree>\examples\EDK\rgb2gray.
The peripheral contains three inputs, which are 32-bit red, green and blue pixel values.
These values are scaled and summed to produce a result that represents the 32-bit
grayscale value. The red, green and blue values are sourced from three shared registers
named 'red', 'green' and 'blue'. The result is written back to a shared register called 'result'.
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2.
Prepare to export the pcore. Drag an EDK processor block into the model. Configure
the processor block by double clicking on the block to bring up the block's dialog box,
as shown below:
Add all available shared memories in the model to the EDK Processor by
verifying/selecting <all> , then click the Add button. As shown above, ensure that the
EDK Processor block has been configured for EDK pcore generation in the Configure
processor for drop-down menu. Dismiss the GUI by clicking the OK button. The EDK
Processor will then create a memory map for the shared memories.
3.
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Expore the pcore. Double click on the System Generator token to open up the System
Generator dialog box. You will use the EDK Export Tool to create the pcore. Options in
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the EDK Export Tool are more fully detailed in the topic System Generator
Compilation Types.:
As shown above, set the Compilation type to be Export as a pcore to EDK. Click on the
Settings... button to open up options for the compilation target. Accept the default settings
so that the pcore is generated and exported into the model's target directory.
Click on the Generate button to initiate the pcore export process.
4.
Integrate the Exported pcore in the XPS
You will now create an XPS project and integrate the pcore into the XPS project.
Information on how to create an XPS project can be found in the topic Using XPS. Follow
the directions there to create an XPS project.
Once the XPS project is created, copy the pcore that is created by System Generator into its
local pcore repository. Since System Generator is instructed to place the pcore inside the
target directory in the previous step, you should find a directory named pcore inside the
target directory. Copy the contents of the directory into the corresponding pcore directory
inside your XPS project. If your XPS project does not contain a pcore directory, create one
before copying.
In the XPS menu, select Project > Rescan User Repositories. The pcore exported by System
Generator, named rgb2gray_plbw, will appear on the list of EDK Peripherals after the
rescan.
Follow the directions in the topic Using XPS for information on how to connect up a pcore
to the MicroBlaze processor in the EDK tool.
After connecting up the pcore, compile the netlist by selecting Hardware > Generate
Netlist.
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Write Software
Create a new software application in your XPS project. Again, information on how to do
this can be found in the topic Using XPS. Add the following code to your application and
compile the software.
#include "xparameters.h"
#include "stdio.h"
#include "xutil.h"
// header file of System Generator Pcore
#include "rgb2gray_plbw.h"
int main (void) {
int i;
uint32_t gray, red, green, blue;
print("-- Entering main() --\n\r");
xc_iface_t *iface;
xc_from_reg_t *fromreg_gray;
xc_to_reg_t *toreg_red, *toreg_green, *toreg_blue;
// initialize the software driver
xc_create(&iface, &RGB2GRAY_PLBW_ConfigTable[0]);
// obtain the memory locations
xc_get_shmem(iface, "result", (void **) &fromreg_gray);
xc_get_shmem(iface, "red",
(void **) &toreg_red);
xc_get_shmem(iface, "green", (void **) &toreg_green);
xc_get_shmem(iface, "blue", (void **) &toreg_blue);
for (i=15; i<30; i++){
red = i;
green = i + 10;
blue = i + 20;
// Write RGB value to peripheral
xc_write(iface, toreg_red->din, red);
xc_write(iface, toreg_green->din, green);
xc_write(iface, toreg_blue->din, blue);
xil_printf("R = 0x%x, G = 0x%x, B = 0x%x -- ",
red, green, blue);
xc_read(iface, fromreg_gray->dout, &gray);
xil_printf("Gray = %x \n\r", gray);
}
print("-- Exiting main() --\n\r");
return 0;
}
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There can be multiple instances of a System Generator pcore in an XPS project. Each of the
instances is associated with a device ID, which can be found in “xparameter.h”. Assume
that the instance of interest has a device ID of 0 based on the following information in
“xparameter.h”.
/* Definitions for driver SG_PLBIFACE */
#define XPAR_SG_PLBIFACE_NUM_INSTANCES 1
/* Definitions for peripheral SG_PLBIFACE_0 */
#define XPAR_SG_PLBIFACE_0_DEVICE_ID 0
Use the device ID of a System Generator pcore instance to select the corresponding item in
RGB2GRAY_PLBW_ConfigTable, which is then provided to xc_create to retrieve the
settings of the specific Systen Generator pcore instance.
The topic Integrating a Processor with Custom Logic contains more information on how
the hardware is wired up and other software issues.
Running the code will produce the following print out on a RS232 terminal.
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Tutorial Example - Designing and Simulating MicroBlaze Processor
Systems
This topic shows an example on how to design and simulate a System Generator model
containing a MicroBlaze processor. A DSP48 co-processor is developed using System
Generator. Using the EDK Processor block, you import a MicroBlaze processor, customized
in Xilinx Platform Studio (XPS), into the System Generator model. You then attach the
DSP48 co-processor to the imported MicroBlaze processor through the automatic memory
mapping mechanisms provided by the EDK Processor block.
This tutorial uses hardware co-simulation to simulate and verify the design. In this case,
the MicroBlaze processor is compiled into hardware, while the DSP48 co-processor model
is left in the System Generator diagram for software simulation. In this example, the
hardware simulation and software simulation communicate with each other using the
point-to-point Ethernet co-simulation technology.
This tutorial example contains the following topics:
•
Create an XPS Project
•
Create a DSP48 Co-Processor Model
•
Import an XPS Project
•
Configure Memory Map Interface
•
Write Software Programs
•
Create a Hardware Co-Simulation Block
•
Create a Testbench Model
•
Update the Co-Simulation Block with Compiled Software
•
Run the Simulation
This example uses the Xilinx Virtex-4 ML402 Evaluation Platform.
The files used in this tutorial can be found a pathname:
<sysgen_tree>\examples\EDK\DSP48CoProcessor, where <sysgen_tree>
denotes the System Generator installation directory.
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Create an XPS Project
First of all, you will need to create a new XPS project, which contains an PLB-based UART
peripheral. A tutorial on how to create a new XPS project can be found in the topic Using
XPS.
Create a DSP48 Co-Processor Model
Copy the DSP48CoProcessorModel found in the folder
<sysgen_tree>\examples\EDK\DSP48CoProcessor into a temporary working
directory, then open the model.
The model contains a DSP48 block with the a, b, and c ports fed from three shared From
Registers with corresponding names. The op port receives signals from a multiplexer
whose select line is sourced from a shared From FIFO named instr.
The output port p of the DSP48 block is sliced and fed into another two shared To Resigers:
the top 16 bits into the overflow register and the bottom 32 bits into the result register.
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Import the XPS Project
In this step, you import an XPS project that contains a MicroBlaze processor into the DSP48
Co-Processor model. Double click on the subsystem called Processor Subsystem and look
into it. In that subsystem, you will find a System Generator token and a blue text box as the
place holder for an EDK Processor block. Open the System Generator block set and drag an
EDK Processor block from the Index library into the Processor Subsystem. Your
augmented subsystem should look like the one shown below:
You will now configure the EDK Processor block to import the XPS project. The import
process will make changes to the XPS project. Thus, ensure that the XPS project is not
currently opened by Xilinx Platform Studio before importing.
Double click on the processor block to bring up the block dialog box. In the Configure
processor for drop-down menu, select HDL netlisting. The Import… button is enabled as
a result of the selection.
Note that the Import… button is disabled when the processor is configured for EDK pcore
generation. In EDK pcore generation mode, it is expected that you will create a pcore in
System Generator and export it to be used in another XPS project. In this case, the
processor is not instanced inside the EDK Processor block. In HDL netlisting mode, it is
expected that you import an XPS project into the System Generator model and netlist it
with other System Generator blocks.
If no XPS project is ever imported, configuring the processor for HDL netlisting will
automatically trigger the launching of the XPS Import Wizard. The XPS Import Wizard can
be launched manually by pressing the Import… button.
In the pop-up file selection dialog, browse to the XPS project created in earlier steps. The
import process starts once a XPS project file (xmp file) is selected. The import process
copies necessary files into the XPS project and changes the project accordingly to allow the
MicroBlaze processor to communicate with the System Generator model.
Note that if there is any software applications contained by the imported XPS project, they
are not compiled during import.
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Configure Memory Map Interface
Re-open the dialog box of the EDK Processor block. Add all the shared memories in the
model to the processor's memory map by selecting <all> in the Available memories pulldown menu and then press the Add button. The EDK Processor block dialog box should
look like the following screenshot. Dismiss the dialog box by clicking the OK button at the
bottom.
Write Software Programs
You will write software programs running on MicroBlaze to read from and write to the
shared memories. Re-open the XPS project in Xilinx Platform Studio. Create a new
software application called MyProject. Make sure that the MyProject software application is
marked for download into BRAM while the other software applications are unmarked.
Refer to the topic Using XPS on how to add a new software application to an EDK project.
Create a new source code file MyProject.c for MyProject and open it in the XPS code
editor.
The above figure shows a portion of the System Assembly View of the XPS project in Xilinx
Platform Studio. A sg_plbiface peripheral is automatically added to an XPS project after it is
successfully imported into System Generator. The sg_plbiface peripheral connects the PLB
bus attached to the imported MicroBlaze processor to the System Generator model
through a memory-mapped interface, and to capture information on how to generate the
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corresponding device software drivers. Right click on sg_plbiface in the System Assembly
View to see its API documentation.
Follow the instructions in the API documentation to include the following header file and
initialize the software driver in MyProject.c.
#include "sg_plbiface.h"
xc_iface_t *iface;
// initialize the software driver
xc_create(&iface, &SG_PLBIFACE_ConfigTable[0]);
Before reviewing the code to run on the processor, first consider how to write data to the a
register on the model. Look at the DSP48 Co-Processor model. Recall that the a port of the
DSP48 block is driven by the output of a shared register by the same name. You want to
write a value to that shared register from with-in MicroBlaze code. By referring to the
driver API, you can see that the shared memory called a is a “To Register” memory type
with xc_to_reg_t access data type, which contains the following data fields:
typedef struct {
xc_w_addr_t din;
uint32_t n_bits;
uint32_t bin_pt;
} xc_to_reg_t;
Once the software driver is initialized, din stores the memory-mapped address of the din
port of the shared memory a, while n_bits and bin_pt store the number of bits and
binary point information.
So in order to write a value to the a shared register, you need to first obtain its settings
through xc_get_shmem and thus:
xc_to_reg_t *toreg_a;
xc_get_shmem(iface, "a",
(void **) &toreg_a);
Note: Calling xc_get_shmem is expensive. You should cache the returned toreg_a for later use
and avoid calling xc_get_shmem multiple times in a program.
You can then use the following single-word write access function to write to the a shared
register:
// -- Set the a port register to 2
xc_write(iface, toreg_a->din, 2);
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The full code of MyProject.c is shown below:
#include "xparameters.h"
#include "stdio.h"
#include "xutil.h"
// header file of System Generator Pcore
#include "sg_plbiface.h"
int main (void) {
uint32_t result, overflow;
char c;
xc_iface_t *iface;
xc_from_reg_t *fromreg_result, *fromreg_overflow;
xc_to_reg_t *toreg_a, *toreg_b, *toreg_c, *toreg_instr;
// initialize the software driver
xc_create(&iface, &SG_PLBIFACE_ConfigTable[0]);
print("Performing p=2*4\r\n");
xc_get_shmem(iface, "result", (void **) &fromreg_result);
xc_get_shmem(iface, "overflow", (void **) &fromreg_overflow);
xc_get_shmem(iface, "a", (void **) &toreg_a);
xc_get_shmem(iface, "b", (void **) &toreg_b);
xc_get_shmem(iface, "c", (void **) &toreg_c);
xc_get_shmem(iface, "instr", (void **) &toreg_instr);
// -- Set the a port register to 2
xc_write(iface, toreg_a->din, 2);
// -- Set the b port register to 4
xc_write(iface, toreg_b->din, 4);
// -- Set the instr register to 2: p=a*b
xc_write(iface, toreg_instr->din, 2);
print("Press a key to read back result\n\r");
c = inbyte();
// -- Read back the result register
xc_read(iface, fromreg_result->dout, &result);
// -- Read back the overflow register
xc_read(iface, fromreg_overflow->dout, &overflow);
xil_printf("Read back: result=%d, overflow=%d\n\r",
result, overflow);
print("Performing p=c+(a:b)\r\n");
// -- Set the a port register to 262140
xc_write(iface, toreg_a->din, 262140);
// -- Set the b port register to 262140
xc_write(iface, toreg_b->din, 262140);
// -- Set the cport register to 1
xc_write(iface, toreg_c->din, 1);
// -- Set the instr register to 3: p=c+(a:b)
xc_write(iface, toreg_instr->din, 3);
print("Press a key to read back result\n\r");
c = inbyte();
// -- Read back the result register
xc_read(iface, fromreg_result->dout, &result);
// -- Read back the overflow register
xc_read(iface, fromreg_overflow->dout, &overflow);
xil_printf("Read back: result=%d, overflow=%d\n\r",
result, overflow);
return 0;
}
Copy and paste the above code into MyProject.c.
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Create a Hardware Co-Simulation Block
The complete Simulink model can be simulated through hardware co-simulation. Make
sure that the shared memories are added into the Memory Maps window and the EDK
Processor block is configured for HDL netlisting. These are required for hardware cosimulation.
Open the dialog box of the System Generator token in the same subsystem as the EDK
Processor block. You generate the hardware co-simulation block from this level of the
model so that only the imported MicroBlaze processor runs in hardware while the rest of
the design is kept in Simulink for software simulation.
Under the Compilation menu select Hardware Co-simulation > ML402 > Ethernet >
Point-to-point. Next, press the Generate button to begin the compilation process. This
may take some time. Upon completion, a hardware co-simulation block is created that
contains a MicroBlaze processor.
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Create a Testbench Model
A testbench model will be created to use the co-simulation block created in the previous
step. Open the DSP48CoProcessor model and delete the Processor Subsystem. Copy the
Processor Subsystem hwcosim block you just generated into the DSP48CoProcessor
model. Save the model as DSP48CoProcessor_testbench.mdl.
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Update the Co-Simulation Block with Compiled Software
Return to the testbench model. Double click on the Processor Subsystem hwcosim block to
bring up the dialog box shown above. To compile the software contained in the XPS project
listed in the Software tab and load it into the hardware co-simulation bitstream, click the
button labeled Compile and update bitstream.
Since Point-to-point Ethernet co-simulation is chosen, you need to configure the Ethernet
interface and also the Configuration interface of the Processor Subsystem hwcosim block.
Select a valid Host interface for your Ethernet communications, and set the configure
interface to Point-to-point Ethernet. Refer to the topic Using Hardware Co-Simulation for
more usage information of the hardware co-simulation block.
Run the Simulation
Before starting the simulation, you need to set up a terminal connected to the COM port of
your computer. This allows for text inputs and outputs to be read from and written to the
MicroBlaze through the RS232 port.
Open up your favorite terminal program. Windows comes with a Hyperterminal
application, which can be found in Start > All Programs > Accessories > Communications
> Hyperterminal. Set up the terminal program to listen to the COM port that you have
wired your RS232 to.
Configure your terminal as follows:
•Baud rate = 115200
•Data = 8 bits
•Parity = none
•Stop = 1 bit
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•Flow control = none
Set the simulation time of the testbench model to inf, allowing enough simulation time for
the MicroBlaze processor to wake up and respond.
Using XPS
This topic provides a quick tutorial on several aspects of the Xilinx Embedded
Development Kit (EDK). Please refer to the EDK documentation for more in depth
explanations and tutorials.
Tutorial Example - Creating a New XPS Project
The Base System Builder is an EDK Wizard to help you construct a fully configured EDK
project. This topic walks you through creating an EDK project configured with a
MicroBlaze Processor, running on a Xilinx ML402 hardware development board.
1.
Launch Xilinx Platform Studio from the Windows start menu
2.
When XPS launches, the following dialog should appear. Select Base System Builder
wizard (recommended), then click OK.
3.
Next, tell Base System Builder that you wish to create a new design by selecting the I
would like to create a new design radio button. Click Next.
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4.
Base System Builder – Select Board. Select the kind of board you want to make use of,
then click Next.
5.
Base System Builder – Select a processor. Next, you are asked to select a processor.
Select MicroBlaze, then click Next.
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6.
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The Configure MicroBlase dialog box is shown below.:
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7.
Base System Builder – Configure IO Interfaces. You only want the RS232 interface. Set
the parameters of the RS232_Uart as shown below, then un-select the other IO
interfaces
8.
Base System Builder – Configure Additional IO Interfaces. The next dialog contains
additional IO interfaces supported by this board. Depending on the board, there may
be multiple dialog pages of "Additional IO Interfaces". At this time, you have no need
for any additional IO interfaces, so un-select them all, then click Next
9.
Base System Builder – Add Internal Peripherals. You have no internal peripherals to
add. Click Next
10. Base System Builder – Software Setup. In this dialog box, you can select the input and
output of STDIN and STDOUT. By default they should be routed to the RS232_Uart.
You may also select to have example code produced in the project for you. Click Next.
11. Base System Builder – System Created. This dialog shows a summary of the options
selected. Click on Generate to cause the EDK project to be created
12. Base System Builder – Finished. This last dialog box shows the files generated. Click
Finish to end the Base System Builder and allow you to continue the EDK flow using
XPS. At this point you have created a basic EDK system.
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Adding a New Software Application
1.
To add a new software application to an EDK Project, first open the EDK project in the
EDK.
2.
In the Project Information Area, click on the Applications tab to reveal the Software
Projects page.
3.
The first item on this page is Add Software Application Project … Double click on this
to bring up the Add Software Application Project dialog box. Type in a project name,
then click OK.
4.
By default, the project is created and not set to be initialized into BRAMS. Make sure to
initialized the project into BRAMS; otherwise, the software code will not be compiled
and added to the bitstream. Also, if you have more than one application, ensure that all
other applications have Marked to Initialize BRAM unchecked.
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5.
Next, create Source or header files. Double click on the Sources branch of a project tree
to cause a File Open Dialog to pop-up. The dialog is rooted at the base location of your
EDK project. It is good to create a directory named after your project and keep your
source and header files there; in this case, MyProject. Create the directory in the same
directory as your EDK.xmp file
Adding a pcore to an EDK Project
1.
Pcores in an EDK project must be in the user repository, or in a directory named pcores,
at the same directory level as the EDK project file
2.
To ensure that the pcore has been loaded, from XPS, select Project > Rescan User
Repositories
3.
Pcores in System Generator are currently FSL-based, so you may use the Configure
Co-processor tool. The tool can be launched from XPS by selecting Hardware >
Configure Coprocessor...
Available FSL-based pcores are listed on the right hand window. Select the relevant pcore,
then click on the Add button. The Configure Coprocessor tool takes care of connecting the
clock and reset signals for the FSL bus, however, any user signals must be wired up by you.
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Using Hardware Co-Simulation
System Generator provides hardware co-simulation, making it possible to incorporate a
design running in an FPGA directly into a Simulink simulation. "Hardware CoSimulation" compilation targets automatically create a bitstream and associate it to a block.
When the design is simulated in Simulink, results for the compiled portion are calculated
in hardware. This allows the compiled portion to be tested in actual hardware and can
speed up simulation dramatically.
Installing Your Hardware Platform
The first step in performing hardware co-simulation is to install and setup your hardware
platform. The following topics provide Specific installation and setup instructions for
Xilinx supported platforms:
Ethernet-Based Hardware Co-Simulation
Installing an ML402 Board for Ethernet Hardware Co-Simulation
Installing an ML506 Board for Ethernet Hardware Co-Simulation
Installing a Spartan-3A DSP 1800A Starter Platform for Ethernet Hardware Co-Simulation
Installing a Spartan-3A DSP 3400A Development Platform for Ethernet Hardware CoSimulation
JTAG-Based Hardware Co-Simulation
Installing an ML402 Board for JTAG Hardware Co-Simulation
Third-Party Hardware Co-Simulation
As part of the Xilinx XtremeDSP™ Initiative, Xilinx works with distributors and many
OEMs to provide a variety of DSP prototyping and development platforms. Please refer to
the following Xilinx web site page for more information on available platforms:
http://www.xilinx.com/technology/dsp/thirdparty_devboards.htm
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Compiling a Model for Hardware Co-Simulation
Once your hardware platform is installed, the starting point for hardware co-simulation is
the System Generator model or subsystem you would like to run in hardware. A model can
be co-simulated, provided it meets the requirements of the underlying hardware platform.
This model must include a System Generator block; this block defines how the model
should be compiled into hardware. The first step in the flow is to open the System
Generator block dialog box and select a compilation type under Compilation.
For information on how to use the System Generator block, see Compiling and Simulating
Using the System Generator Block.
Choosing a Compilation Target
You may choose the hardware co-simulation platform by selecting an appropriate
compilation type in the System Generator block dialog box. Hardware co-simulation
targets are organized under the Hardware Co-Simulation submenu in the Compilation
dialog box field.
When a compilation target is selected, the fields on the System Generator block dialog box
are automatically configured with settings appropriate for the selected compilation target.
System Generator remembers the dialog box settings for each compilation target. These
settings are saved when a new target is selected, and restored when the target is recalled.
Invoking the Code Generator
The code generator is invoked by pressing the Generate button in the System Generator
block dialog box.
The code generator produces a FPGA configuration bitstream for your design that is
suitable for hardware co-simulation. System Generator not only generates the HDL and
netlist files for your model during the compilation process, but it also runs the downstream
tools necessary to produce an FPGA configuration file.
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Note: A status dialog box (shown below) will appear after you press the Generate button. During
compilation, the status box provides a Cancel and Show Details button. Pressing the Cancel button
will stop compilation. Pressing the Show Details button exposes details about each phase of
compilation as it is run. It is possible to hide the compilation details by pressing the Hide Details
button on the status dialog box.
The configuration bitstream contains the hardware associated with your model, and also
contains additional interfacing logic that allows System Generator to communicate with
your design using a physical interface between the platform and the PC. This logic
includes a memory map interface over which System Generator can read and write values
to the input and output ports on your design. It also includes any platform-specific
circuitry (e.g., DCMs, external component wiring) that is required for the target FPGA
platform to function correctly.
Hardware Co-Simulation Blocks
System Generator automatically creates a new hardware co-simulation block once it has
finished compiling your design into an FPGA bitstream. A Simulink library is also created
in order to store the hardware co-simulation block. At this point, you can copy the block
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out of the library and use it in your System Generator design as you would other Simulink
and System Generator blocks.
The hardware co-simulation block assumes the external interface of the model or
subsystem from which it is derived. The port names on the hardware co-simulation block
match the ports names on the original subsystem. The port types and rates also match the
original design.
Hardware co-simulation blocks are used in a Simulink design the same way other blocks
are used. During simulation, a hardware co-simulation block interacts with the underlying
FPGA platform, automating tasks such as device configuration, data transfers, and
clocking. A hardware co-simulation block consumes and produces the same types of
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signals that other System Generator blocks use. When a value is written to one of the
block's input ports, the block sends the corresponding data to the appropriate location in
hardware. Similarly, the block retrieves data from hardware when there is an event on an
output port.
Hardware co-simulation blocks may be driven by Xilinx fixed-point signal types, Simulink
fixed-point signal types, or Simulink doubles. Output ports assume a signal type that is
appropriate for the block they drive. If an output port connects to a System Generator
block, the output port produces a Xilinx fixed-point signal. Alternatively, the port
produces a Simulink data type when the port drives a Simulink block directly.
Note: When Simulink data types are used as the block signal type, quantization of the input data is
handled by rounding, and overflow is handled by saturation.
Like other System Generator blocks, hardware co-simulation blocks provide parameter
dialog boxes that allow them to be configured with different settings. The parameters that
a hardware co-simulation block provides depend on the FPGA platform the block is
implemented for (i.e., different FPGA platforms provide their own customized hardware
co-simulation blocks).
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Hardware Co-Simulation Clocking
Selecting the Target Clock Frequency
If you are using a Xilinx ML402 or ML506 platform, System Generator allows you to
choose a clock frequency for the target design that is equal to or less than the system clock
frequency. The following table outlines the frequencies that are available:
Platform
Xilinx ML402
Interface
JTAG,
Point-to-point Ethernet,
Network-based Ethernet
System Clock
Frequency
100 MHz
Available
Frequencies
100 MHz
66.7 MHz
50 MHz
33.3 MHz
Xilinx ML506
Point-to-point Ethernet,
Network-based Ethernet
200 MHz
100 MHz
66.7 MHz
50 MHz
33.3 MHz
As shown below, you set the target clock frequency at compilation time, by clicking the
Settings button on the System Generator block dialog box, then select the frequency in the
pulldown menu.
1. Click
2. Select
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Clocking Modes
There are several ways in which a System Generator hardware co-simulation block can be
synchronized with its associated FPGA hardware. In single-step mode, the FPGA is in
effect clocked from Simulink, whereas in free-running clock mode, the FPGA runs off an
internal clock, and is sampled asynchronously when Simulink wakes up the hardware cosimulation block.
Single-Step Clock
In single-step clock mode, the hardware is kept in lock step with the software simulation.
This is achieved by providing a single clock pulse (or some number of clock pulses if the
FPGA is over-clocked with respect to the input/output rates) to the hardware for each
simulation cycle. In this mode, the hardware co-simulation block is bit-true and cycle-true
to the original model.
Because the hardware co-simulation block is in effect producing the clock signal for the
FPGA hardware only when Simulink awakes it, the overhead associated with the rest of
the Simulink model's simulation, and the communication overhead (e.g. bus latency)
between Simulink and the FPGA platform can significantly limit the performance
achieved by the hardware. As a general rule of thumb, as long as the amount of
computation inside the FPGA is significant with respect to the communication overhead
(e.g. the amount of logic is large, or the hardware is significantly over-clocked), the
hardware will provide significant simulation speed-up.
Free-Running Clock
In free-running clock mode, the hardware runs asynchronously relative to the software
simulation. Unlike the single-step clock mode, where Simulink effectively generates the
FPGA clock, in free-running mode, the hardware clock runs continuously inside the FPGA
itself.
In this mode, simulation is not bit and cycle true to the original model, because Simulink is
only sampling the internal state of the hardware at the times when Simulink awakes the
hardware co-simulation block. The FPGA port I/O is no longer synchronized with events
in Simulink. When an event occurs on a Simulink port, the value is either read from or
written to the corresponding port in hardware at that time. However, since an unknown
number of clock cycles have elapsed in hardware between port events, the current state of
the hardware cannot be reconciled to the original System Generator model. For many
streaming applications, this is in fact highly desirable, as it allows the FPGA to work at full
speed, synchronizing only periodically to Simulink.
In free-running mode, you must build explicit synchronization mechanisms into the
System Generator model. A simple example is a status register, exposed as an output port
on the hardware co-simulation block, which is set in hardware when a condition is met.
The rest of the System Generator model can poll the status register to determine the state of
the hardware.
Selecting the Clock Mode
Not every hardware platform supports a free running clock. However, for those that do,
the parameters dialog box for the hardware co-simulation block provides a means to select
the desired clocking mode. You may change the co-simulation clocking mode before
simulation starts by selecting either the Single stepped or Free running radio button
under the Clocking etch box.
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Note: The clocking options available to a hardware co-simulation block depend on the FPGA
platform being used (i.e., some platforms may not support a free-running clock source, in which case
it is not available as a dialog box parameter).
Board-Specific I/O Ports
FPGA platforms often include a variety of on-board devices (e.g., external memory, analog
to digital converters, etc.) that the FPGA can communicate with. For a variety of reasons, it
may be useful to form connections to these components in your System Generator models,
and to use these components during hardware co-simulation. For example, if your board
includes external memory, you may want to define the control and interface logic to this
memory in your System Generator design, and use the physical memory during hardware
co-simulation.
You can interface to these types of components by including board-specific I/O ports in
your System Generator models. A board-specific port is a port that is wired to an FPGA
pad when the model is compiled for hardware co-simulation. Note that this type of port
differs from standard co-simulation ports that are controlled by a corresponding port on a
hardware co-simulation block.
A board-specific I/O port is implemented using special non-memory mapped gateway blocks
that tell System Generator to wire the signals to the appropriate FPGA pins when the
model is compiled into hardware. To connect a System Generator signal to a board-specific
port, connect the appropriate wire to the special gateway (in the same way as is done for a
traditional gateway).
Non-memory mapped gateways that are common to a specific device are often packaged
together in a Simulink subsystem or library. The XtremeDSP Development Kit, for
example, provides a library of external device interface subsystems, including analog to
digital converters, digital to analog converters, LEDs, and external memory. The interface
subsystems are constructed using Gateways that specify board-specific port connections.
These subsystems are treated like other System Generator subsystems during simulation
(i.e., they perform double precision to Xilinx fixed-type conversions). When System
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Generator compiles the design into hardware, it connects the signals that are associated
with the Gateways to the appropriate external devices they signify in hardware.
I/O Ports in Hardware Co-simulation
A hardware co-simulation block does not include board-specific ports on its external
interface. This means that if a model includes a gateway that corresponds to a boardspecific port, the corresponding port is connected to the simulation model instead of the
actual hardware when the design is compiled for hardware co-sim. To leave the port
connected to a real port, use a non-memory mapped gateway instead. See the topic on nonmemory-mapped ports Supporting New Platforms.
Ethernet Hardware Co-Simulation
System Generator provides hardware co-simulation interfaces that facilitate highthroughput communication with an FPGA platform over an Ethernet connection. These
interfaces eliminate the communication range limitation imposed by programming cable
solutions, while also offering superior bandwidth for real-time applications. By supporting
device configuration over Ethernet, there is no need for a separate programming cable.
Two flavors of Ethernet hardware co-simulation are supported by the tool. Point-to-point
Ethernet co-simulation provides a straightforward high-performance co-simulation
environment using a direct, point-to-point Ethernet connection between a PC and FPGA
platform. Network-based Ethernet Co-Simulation allows communication with a remote
FPGA through the widely deployed IPv4 network infrastructure.
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Point-to-Point Ethernet Hardware Co-Simulation
Point-to-point Ethernet Hardware Co-simulation provides a co-simulation interface using
a raw Ethernet connection. The raw Ethernet connection refers to a Layer 2 (a.k.a. DataLink Layer) Ethernet connection, between a supported FPGA development board and a
host PC, with no network routing equipment along the path. By taking the advantage of
the ubiquity and advancement of Ethernet technologies, the interface facilitates a
convenient and high-bandwidth co-simulation to an external FPGA device.
Interface Features
The interface supports 10/100/1000 Mbps half/full duplex modes. Jumbo Frame is also
supported on a Gigabit Ethernet, provided it is enabled by the underlying connection. For
FPGA device configuration, the interface supports either JTAG-based configuration over a
Xilinx Parallel Cable IV or a Xilinx Platform USB cable, or Ethernet-based configuration
over the same Point-to-point Ethernet connection for co-simulation.
Note: This co-simulation interface utilizes an evaluation version of the Ethernet MAC core. Because
this is an evaluation version of the core, it will become dysfunctional after continuous, prolonged
operation (e.g., around 7 hours) in the target FPGA. Operation of the core will restart with a new
simulation. For more information about obtaining the full version of the core, please visit the product
page at http://www.xilinx.com/xlnx/xebiz/designResources/ip_product_details.jsp?key=TEMAC.
Supported FPGA Development Platforms
Development platforms that support point-to-point ethernet hardware co-simulation are
listed in the topicEthernet-Based Hardware Co-Simulation. Links to the appropriate
platform installation instructions are also provided.
Configuring Co-Simulation Block Parameters
There are several block parameters specific to the Point-to-point Ethernet co-simulation
interface. The rest of this topic describes step-by-step how to configure the parameters of
the Point-to-point Ethernet co-simulation block. Refer to the topic Point-to-point Ethernet
Co-Simulation in the Xilinx Block section for details of all the block parameters.
1.
Use the Basic tab to select the appropriate clock source for the co-simulation.
Select a Clock
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Use the Configuration tab to select the Configuration Method:
♦
For the Download cable panel, choose Point-to-point Ethernet.
♦
For JTAG-based download cables (Parallel Cable IV or Platform USB), change
the cable speed if the default value is not suitable for the cable in use.
♦
Change the Configuration timeout (ms) value only when necessary. The default
value should suffice in most cases. A larger value is needed when it takes a
considerable amount of time to re-establish a network connection with the FPGA
platform after device configuration completes.
♦
If there is a Video I/O daughter card attached to the ML402 board, select Video
I/O Daughter Card (VIODC) from the Configuration profile pulldown menu
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3.
Use the Ethernet tab to configure the Ethernet Interface Settings:
Select an Interface
♦
From the Host interface panel, use the pulldown list to select the appropriate
network interface for co-simulation.
Note: The pull down list only shows those Ethernet-compatible network interfaces installed
on the host, which support 10/100/1000 Mbps, and are currently enabled and attached to an
active Ethernet segment. If the target interface is not listed as expected, examine the
connection and click the Refresh button to update the list.
♦
4.
The information box beneath the pull-down list provides the details about the
selected interface. Examine the information to ensure the appropriate interface is
chosen, and adjust the network settings in the operating system when necessary.
Depending on which configuration method is chosen, the MAC address in the FPGA
interface panel may need to be changed.
a.
For Point-to-point Ethernet-based configuration:
Observe the MAC address displayed on the LCD screen of the target board when the
configuration boot-loader is running. Change the FPGA MAC address in the cosimulation block if the default value does not match the target board. Refer to Optional
Step to set the Ethernet MAC Address and the IPv4 Address for details about
assigning the MAC address on a ML402 board.
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Note: The MAC address must be specified using six pairs of two-digit hexadecimal number
separated by colons (for example, 00:0a:35:11:22:33).
Co-Simulating the Design
After setting the block parameters appropriately, you may begin co-simulation by pressing
the Simulink Start button. System Generator automates the device configuration process
and transfers the design under test (DUT) into the FPGA device for co-simulation. A dialog
box will be shown to describe the status of the process.
1.
The final configuration file is first generated based on the input bitstream specified in
the block parameters.
2.
The final configuration file is then transferred to the target board using the selected
download cable, and used to configure the FPGA device. The progress of
configuration is shown in the dialog box when the configuration is performed over a
Point-to-point Ethernet connection.
3.
Upon the completion of device configuration, the co-simulation engine re-establishes
the connection to the target board, and starts co-simulating the design.
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Known Issues
•
If you encounter problems transmitting data over a point-to-point Ethernet
connection or experience instability issues, please disable the Hyper-Threading
option in the BIOS on an Intel platform.
•
IP fragmentation is not supported by the network-based Ethernet configuration.
Please ensure the connection established between the host and the target FPGA
platform can handle a maximum transmission unit (MTU) size of at least 1300 bytes
without fragmentation.
Network-Based Ethernet Hardware Co-Simulation
Interface Features
The interface supports operations in 10/100/1000 Mbps half/full duplex modes. For
FPGA device configuration, the interface supports Ethernet-based configuration over the
same network connection for co-simulation. This means that a separate programming
cable (e.g., Parallel Cable IV) is not required.
Note: This co-simulation interface utilizes an evaluation version of the Ethernet MAC core. Because
this is an evaluation version of the core, it will become dysfunctional after continuous, prolonged
operation (e.g., around 7 hours) in the target FPGA. Operation of the core will restart with a new
simulation. For more information about obtaining the full version of the core, please visit the product
page at http://www.xilinx.com/xlnx/xebiz/designResources/ip_product_details.jsp?key=TEMAC.
Supported FPGA Development Boards
The Xilinx ML402 and ML506 development platform is currently supported for the
network-based Ethernet co-simulation.
Setup Procedures
1.
Network-based Ethernet co-simulation performs device configuration over the
network configuration. Before using network configuration, you must ensure the IP
address, MAC address, and configuration server are properly setup on the System
ACE CompactFlash. Refer to the topic Optional Step to set the Ethernet MAC Address
and the IPv4 Address for information on how to do this.
2.
The target FPGA listens on the UDP port 9999. Please ensure the underlying network
does not block the associated traffic.
Known Issues
IP fragmentation is not supported by the network-based Ethernet co-simulation interface.
Please ensure the connection established between the host and the target FPGA platform
can handle a maximum transmission unit (MTU) size of at least 1300 bytes without
fragmentation.
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Shared Memory Support
System Generator's hardware co-simulation interfaces allow shared memory blocks and
shared memory block derivatives (e.g., Shared FIFO and Shared Registers) to be compiled
and co-simulated in FPGA hardware. These interfaces make it possible for hardware-based
shared memory resources to map transparently to common address spaces on the host PC.
When applied to System Generator co-simulation hardware, shared memories can help
facilitate high-speed data transfers between the host PC and FPGA, and further bolster the
tool's real-time hardware co-simulation capabilities. This topic describes how shared
memories can be used within the context of System Generator's hardware co-simulation
framework.
Compiling Shared Memories for
Hardware Co-Simulation
Describes how to compile a System Generator
design for hardware co-simulation when the
design contains shared memory blocks.
Co-Simulating Unprotected
Shared Memories
Describes how shared memory blocks
configured with unprotected access mode
behave during hardware co-simulation.
Co-Simulating Lockable Shared
Memories
Describes how shared memory blocks
configured with lockable access mode behave
during hardware co-simulation.
Co-Simulating Shared Registers
Describes how to compile a System Generator
design for hardware co-simulation when the
design contains shared Registers.
Co-Simulating Shared FIFOs
Describes how to compile a System Generator
design for hardware co-simulation when the
design contains shared FIFOs.
Restrictions on Shared Memories
Lists the restrictions that are imposed when
using shared memory blocks with hardware cosimulation.
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Compiling Shared Memories for Hardware Co-Simulation
System Generator allows shared memory and shared memory derivative (e.g., shared
FIFO and shared register) blocks to be compiled for hardware co-simulation. Designs that
include shared memories are compiled for hardware co-simulation the same way
traditional System Generator designs are compiled – by selecting a compilation target and
pressing the Generate button on the System Generator dialog box. A design containing
shared memory blocks may be compiled for hardware co-simulation provided the
requirements described in the topic Restrictions on Shared Memories are satisfied.
When a shared memory is compiled for hardware co-simulation, it is implemented in
hardware either by a core or HDL component. The table below shows how shared memory
blocks are mapped to hardware implementations
To Block
From Block
Hardware Implementation
Shared Memory
Shared Memory
Dual Port Block Memory 6.1
To FIFO
To FIFO
Fifo Generator 2.1
To Register
To Register
synth_reg_w_init.(vhd,v)
There are two ways in which shared memories are compiled for hardware co-simulation.
The type of compilation depends on whether the shared memory name is unique in the
design, or if the shared memory has a partner who shares the same name. The following
topics describe the two types of compilation behavior.
Single Shared Memory Compilation
A shared memory block is considered "single" if it has a unique name within a design.
When a single shared memory is compiled for hardware co-simulation, System Generator
builds the other half of the memory and automatically wires it into the resulting netlist.
Additional interfacing logic is attached to the memory that allows it to communicate with
the PC. When you co-simulate the shared memory, one half of the memory is used by the
logic in your System Generator design. The other half communicates with the PC
interfacing logic as shown in the figure below. In this manner, it is possible to communicate
with the shared memory embedded inside the FPGA while a simulation is running.
The shared memory hardware and interface logic are completely encapsulated by the
hardware co-simulation block that is generated for the design. By co-simulating a
hardware co-simulation block that contains a shared memory, it is possible for your design
logic and host PC software to share a common address space on the FPGA.
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Note: The name of the hardware shared memory is the same as the shared memory name used by
the original shared memory block. For example, if a shared memory block uses "my_memory," the
hardware implementation of the block can be accessed using the "my_memory" name.
All shared memories embedded inside the FPGA are automatically created and initialized
before the start of a simulation by their respective co-simulation blocks. This means that
any other shared memory objects that wish to access the hardware shared memory must
specify Ownership and initialization parameter as Owned and initialized elsewhere.
Doing so causes the software-based shared memories to attach automatically to the shared
memories that reside inside the FPGA.
Compiling Shared Memory Pairs
It is also possible to compile a shared memory pair (i.e., two shared memories that specify
the same name) for hardware co-simulation. In this case, the two shared memory halves
are merged into a single hardware implementation during compilation. Unlike single
shared memories, both sides of a shared memory pair connect to System Generator user
design logic. For example, the figure below shows the hardware implementation for a To /
From FIFO shared memory pair.
Note that because both sides of the shared memory connect to user design logic, it is not
possible to communicate with these shared memories directly from the host PC.
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Viewing Shared Memory Information
Hardware co-simulation blocks allow you to view information about the shared memories
that were compiled as part of the design. A hardware co-simulation block that contains
shared memories will have an enabled Shared Memories tab in the block configuration
dialog box shown below. Clicking on this tab exposes a table of information about each
shared memory in the design.
The shared memory information table describes the type, bit width, and depth of each
shared memory in the design. For Shared Memory blocks, it also specifies the Access
Protection mode. Clicking on the [+] or [-] symbol next to the shared memory icon expands
or collapses the shared memory table, respectively.
The icons associated with each shared memory type are shown in the table below.
Memory Type
Icon
Shared Memory
Shared FIFO
Shared Register
Co-Simulating Unprotected Shared Memories
Unprotected shared memory blocks may be written to or read from at any time – this type
of memory has no notion of mutually exclusive access. Data transfers to and from an
unprotected hardware shared memory occur a single-word at a time, unlike the highspeed data transfer mode used by lockable shared memories. To ensure data coherency
between software and hardware, a single image of the shared memory data is shared
between hardware and software. This image is stored in the FPGA using dual port
memory. System Generator allows both hardware design logic and other software-based
shared memory objects on the host PC to access the shared memory data concurrently.
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When software shared memory objects read or write data to the shared memory, a proxy
seamlessly handles communication with the hardware memory resource.
The following figure shows an example of unprotected shared memory implemented in
the FPGA that is communicating with three shared memory objects running on the host
PC. In this example, the software shared memory objects access the hardware shared
memory by specifying the same shared memory name, my_mem. From the perspective of
the software shared memories, the implementation of the shared memory resource is
irrelevant; the hardware shared memory is treated as any another shared memory object.
Read and writes to the shared memory are handled by the shared memory API.
Note: Not all shared memory objects need to be created or executed in the Simulink environment.
The C++ application in the figure below is just one example of an external application that may
communicate with the hardware shared memory data using the shared memory API.
Co-Simulating Lockable Shared Memories
In lockable access mode, the System Generator co-simulation hardware must acquire lock
over the shared memory object before it may access its contents. When the hardware
acquires (releases) lock of the shared memory, the memory contents are transferred to
(from) the FPGA using a high-speed data transfer. Using this methodology, it is possible to
implement System Generator hardware co-simulation designs with high memory
bandwidth requirements. For more information on how to do this, refer to the tutorial
entitled Real-Time Signal Processing using Hardware Co-Simulation.
Unlike unprotected shared memories, two images of the shared memory data are used
when a lockable shared memory is co-simulated. One memory image is stored using dual
port memory in the FPGA. This image is accessed by the System Generator hardware cosimulation design and co-simulation interfacing logic. The other image is implemented as
a shared memory object on the host PC. This software shared memory image is accessed by
any software shared memory objects used in a design.
In lockable mode, a software process or hardware circuit that wishes to access the shared
memory must first obtain the lock. If the hardware has lock of the memory, no software
objects may access the memory contents. Likewise, if a software object controls the
memory, the hardware cannot read or write to the memory. Note that lockable hardware
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shared memories include additional logic to handle the mutual exclusion. The interaction
between hardware and software lockable shared memories is shown in the figure below: .
The red circle in the figure above represents a lock token. This token may be passed to any
shared memory object, regardless of whether it is implemented in hardware or software.
The dashed circle represents lock placeholders and signifies that lock can be passed to the
block it is associated with. The diamond in the figure above represents a modifiable token.
This token illustrates that when hardware has lock of the memory, the hardware shared
memory image may be modified. Likewise, when a software shared memory object has
lock, the software shared memory image may be modified.
Having two shared memory images requires synchronization between software and
hardware to ensure the images are coherent. This synchronization is accomplished by
transferring the memory image between software and hardware upon lock transfer.
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System Generator performs high speed data transfers between the host PC and FPGA. The
semantics associated with these transactions are shown in the figure below. .
Co-Simulating Shared Registers
A To Register, From Register or shared register pair may be generated and co-simulated in
FPGA hardware. Here and throughout this topic, a shared register pair is defined as a To
Register block and From Register block that specify the same name (e.g., 'Bar'). In
hardware, a shared register is implemented using a synthesizable register component (for
VHDL) or a module (for Verilog). This topic explains how single shared registers and
shared register pairs behave during hardware co-simulation.
When a design that includes a shared register pair is compiled for hardware co-simulation,
the pair is replaced by a single register instance. Both sides of the register attach to user
design logic; that is, logic that originated from the original System Generator model.
Unlike designs compiled using the Multiple Subsystem Generator block, all ports on the
hardware register attach to signals in the same clock domain. In this case, control of the
register is not shared between the PC and FPGA hardware since all register ports are
attached to user design logic. Compiling a shared register pair into hardware is equivalent
to compiling a System Generator Register or Delay block.
Compiling a single To Register or From Register block for hardware co-simulation results
in a different type of implementation. A single register is still created to replace the To or
From Register block. Only in this case, the register connects to both the PC interface and
FPGA logic. The side of the register in the original model remains connected to user design
logic. The other side of the register attaches to data and control ports that interface with the
PC.
For example, in the following figure, when a From Register block is compiled for hardware
co-simulation, the dout register port remains attached to the user design. The din, ce, and
clk register ports attach to control and data ports that interface with the PC. In this way, it
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is possible for the PC to write to the register using System Generator's hardware cosimulation interfaces.
When a To Register block is compiled for hardware co-simulation, as shown in the figure
below, the input ports are wired to user logic while the output port is wired to PC interface
logic. You may access a shared register during hardware co-simulation using the other half
of the shared register (i.e., using a To or From Register block), a C program or executable
(System Generator API), or a MATLAB program.
For designs that use hardware co-simulation, shared register pairs are typically distributed
between software and FPGA hardware. In other words, one half of the pair is implemented
in the FPGA while the other half is simulated in software using a To or From Register
block. When data is written to a software To Register block, the hardware register is
updated to with the same data. Similarly, when data is written into the hardware register,
the same data is read by the From Register software block. A software shared register may
connect to a hardware shared register simply by specifying the name of the shared register
as it was compiled for hardware co-simulation.
Note: You may find the names of all shared memories embedded inside an FPGA co-simulation
design by viewing the Shared Memories tab on a hardware co-simulation block.
When a software / hardware shared memory pair is co-simulated, System Generator
transparently manages the interaction between the PC and FPGA hardware. This means
that a shared register pair simulated in software should behave the same as a shared
register pair distributed between the PC and FPGA hardware.
Co-Simulating Shared FIFOs
A To FIFO, From FIFO or shared FIFO pair may be generated and co-simulated in hardware.
Here and throughout this topic, a shared FIFO pair is defined as a To FIFO block and From
FIFO block that specify the same name (e.g., 'Bar'). In hardware, a shared FIFO is
implemented using the FIFO Generator core. The core is configured to use independent
(asynchronous) clocks, and block memory for data storage. This topic explains why cosimulating shared FIFOs is useful, and also how these blocks behave in hardware.
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Asynchronous FIFOs are typically used in multi-clock applications to safely cross clock
domain boundaries. When a Free-Running Clock mode is used for hardware cosimulation, the FPGA operates asynchronously relative to the Simulink simulation. That is,
the FPGA is not kept in lockstep with the simulation. Using the Free-Running Clock mode
effectively establishes two clock domains: the Simulink simulation clock domain and the
FPGA free-running clock domain. In these designs, Shared FIFOs provide a reliable and
safe way to transfer data between the host PC and FPGA platform.
Shared FIFOs may also be used to support burst transfers during co-simulation. It is
possible to create vectors or frames of data, and transfer the data to the FPGA in a single
transaction with the hardware. These interfaces can be used to further accelerate
simulation speeds beyond what is typically possible with hardware co-simulation. For
more information on how this is accomplished, refer to the topic Frame-Based Acceleration
using Hardware Co-Simulation.
When a shared FIFO pair is generated for co-simulation, a single asynchronous FIFO core
replaces the two software shared FIFO blocks. As shown in the figure below, the read /
write FIFO sides are attached to user design logic (i.e., logic derived from the original
System Generator model) that attached to the From FIFO and To FIFO blocks. Because both
FIFO sides attach to user logic in hardware, the PC does not share control of the FIFO with
the design. Instead, the FIFO behavior is similar to a System Generator design that
includes a traditional FIFO block.
Note that even though the FIFO exposes independent clock ports, the same co-simulation
clock drives both ports when a FIFO pair is compiled. This is different from compiling a
shared FIFO pair using the Multiple Subsystem Generator block, where the clocks are from
distinct clock domains.
Single shared FIFO blocks are treated differently than shared FIFO pairs. A single To FIFO
or From FIFO block is replaced by an asynchronous FIFO core when it is compiled for
hardware co-simulation. One side of the FIFO (i.e., the unused shared FIFO half in System
Generator) is connected to PC interface logic. The other side is connected to user design
logic that attached to the original To or From FIFO block. In this manner, control over the
FIFO is distributed between the PC and FPGA design.
As shown in the following figure, when a To FIFO block is compiled for hardware cosimulation, the write side of the FIFO is connected to the same logic that attached to To
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FIFO block in user design. The read side of the FIFO is connected to PC interface logic that
allows the PC to read data from the FIFO during simulation.
In the figure below, the opposite wiring approach is used when a From FIFO block is
compiled for hardware co-simulation. In this case, the write side of the FIFO is connected
to PC interface logic, while the read side is connected to the user design logic. The host PC
writes data into the FIFO and the design logic may read data from the FIFO.
For designs that use hardware co-simulation, shared FIFO pairs are typically distributed
between software and FPGA hardware. In other words, one half of the pair is implemented
in the FPGA while the other half is simulated in software using a To or From FIFO block.
Together, the software and hardware portions form a fully functional asynchronous FIFO.
When a software / hardware shared FIFO pair is co-simulated, System Generator
transparently manages the necessary transactions between the PC and FPGA hardware.
When data is written to a software To FIFO block during simulation, the same data is
written to the FIFO in hardware. The design in hardware may then retrieve this data by
reading from the FIFO. Similarly, when data is written into the hardware FIFO by design
logic, the data may be read by the From FIFO software block. Note that the empty, full, read
and write count ports on the shared FIFO blocks pessimistically reflect the state of the
hardware FIFO counterpart. A software shared FIFO may connect to a hardware shared
FIFO simply by specifying the name of the shared FIFO as it was compiled for hardware
co-simulation.
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Specifying Xilinx Tool Flow Settings
Note: You may find the names of all shared memories embedded inside an FPGA co-simulation
design by viewing the Shared Memories tab on a hardware co-simulation block.
Restrictions on Shared Memories
The following restrictions apply to System Generator designs that use shared memory,
register, or FIFO blocks in conjunction with hardware co-simulation:
•
The access protection mode of a shared memory may not be modified once it has been
compiled for hardware co-simulation.
•
Shared memory address port widths are limited to 24-bits (or less), allowing an
address space of 16,777,216 words;
•
Shared memory, register, and FIFO data port widths are currently limited to 32-bits or
less.
•
Shared memories and FIFOs are implemented in hardware using block memories;
neither distributed nor external memory implementations are currently supported.
•
No more than two shared memories with the same shared memory name may be
compiled for hardware co-simulation.
•
Two or more hardware co-simulation blocks that have shared memory names in
common may not concurrently be used in the same design.
Specifying Xilinx Tool Flow Settings
When a design is compiled for System Generator hardware co-simulation, the command
line tool, XFLOW, is used to implement and configure your design for the selected FPGA
platform. XFLOW defines various flows that determine the sequence of programs that
should be run on your design during compilation. There are typically multiple flows that
must be run in order to achieve the desired output results, which in the case of hardware
co-simulation targets, is a configuration bitstream.
System Generator uses two flows, implementation and configuration, in order to produce a
configuration bitstream. The implementation flow is responsible for compiling the
synthesis tool netlist output (e.g., EDIF or NGC) into a placed and routed NCD file. To
accomplish this, it runs the Xilinx tools NGDBuild, MAP, and PAR. The implementation
flow can also execute TRACE (for timing analysis purposes), although this program is
typically omitted in order to expedite the compilation process. The configuration flow runs
the tools necessary to create an FPGA bitstream, using the fully elaborated NCD file as
input.
The implementation and configuration flow types have separate XFLOW options files
associated with them. An XFLOW options file declares the programs that should be run for
a particular flow, and defines the command line options that are used by these tools. Each
hardware co-simulation compilation target provides options files that define the default
configuration options for these tools. Sometimes you may want to use options files that use
settings that differ (e.g., to specify a higher placer effort level in PAR) from the default
options provided by the target. In this case, you may create your own options files, or edit
the default options files to include your desired settings.
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The Hardware Co-Simulation Settings dialog box, shown below, allows you to specify
options files other than the default options files provided by the compilation target.
Parameters available on the Hardware Co-Simulation Settings GUI are:
•
Implementation Flow: Specifies the options file that is used by the implement flow
type. By default, System Generator will use the implement options file that is
specified by the compilation target.
•
Configuration Flow: Specifies the options file that is used by the config flow type. By
default, System Generator will use the config options file that is specified by the
compilation target.
The Xilinx ISE software includes several example XFLOW options files. From the base
directory of your Xilinx ISE software tree (e.g., c:\Xilinx\), these files are located under the
directory xilinx\data (e.g., C:\Xilinx\xilinx\data). Three commonly used
implementation options files include:
•
balanced.opt
•
fast_runtime.opt
•
high_effort.opt
Note: It is possible to define options files that may cause errors in the System Generator hardware
co-simulation flow. As a result, it is typically a good idea to make backup copies of the default options
files before modifying them. In addition, the configuration options file should be edited with caution, as
most FPGA hardware platforms have specific configuration parameter requirements.
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Frame-Based Acceleration using Hardware Co-Simulation
With the tremendous growth in programmable device size and computational power,
lengthy simulation times have become an expected, yet undesirable part of life for most
engineers. Depending on the design size and complexity, the required simulation time can
be quite large, sometimes on the order of days to run to completion. This problem is
exacerbated by the fact that most systems must be simulated many times before the design
is considered functional and ready for deployment. Fortunately, System Generator for DSP
provides hardware co-simulation interfaces that allow you to dramatically accelerate
simulation speeds of your FPGA designs.
There are several factors that influence exactly how much acceleration can be gained by
using hardware co-simulation. These considerations include the size of the design, the
number of ports on the model, and the hardware over-sampling rate. Under normal
operation, the PC communicates with the FPGA during each Simulink simulation cycle.
These software / hardware transactions often involve significant overhead and can end up
being the limiting factor in simulation performance. Also of importance is the cosimulation interface being used. Some interfaces (e.g., PCI) are faster than others (e.g.,
JTAG). For a reasonably large design, the typical simulation is accelerated by an order of
magnitude when co-simulated in hardware.
Keeping the above points in mind, there are ways to further bolster simulation
performance. Remember that every time the PC interacts with hardware, there is an
overhead cost that impacts simulation performance. One of the ways the number of FPGA
transactions can be mitigated is by utilizing Simulink vector and frame signal types. Here
and throughout the rest of this tutorial, FPGA transactions involving Simulink vector and
frame signals as simply referred to as vector transfers. This idea is straightforward –
bundle as many input data samples together as possible and have the FPGA process the
data in a single transaction. Fewer transactions with the FPGA results in better simulation
performance.
In this tutorial, Simulink vector and frame signals are used to increase simulation
performance beyond what is traditionally possible with hardware co-simulation. A stepby-step example filter design is presented to help illustrate these concepts. By using the
techniques described in this tutorial, it is possible to further increase simulation
performance, sometimes by as much as two orders of magnitude over software-based
simulations.
Before diving into the details, it is worth exploring exactly what you are trying to
accomplish from a high-level perspective. In summary, you will do the following during a
Simulink simulation cycle:
•
Buffer a series of scalar input data values into a Simulink vector;
•
Transfer the vector data to a buffer residing on the FPGA using a burst transfer;
•
Use the FPGA, in free-running clock mode, to sequentially process the entire input
buffer;
•
Use the FPGA to write the data into an output buffer;
•
Transfer the contents of the output buffer back into Simulink and reconstruct the data
as a Simulink vector;
•
Unbuffer the vector into a series of output scalar values.
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Shared Memories
Before a System Generator design can support vector transfers, it must be augmented with
appropriate input and output buffers. In hardware, these buffers are implemented using
internal memory (e.g., BRAMs) and are used to store vectors of simulation data that are
written to and read from the FPGA by the PC. This means that the maximum size of the
buffers is limited by the amount of internal memory available on the target device. In
System Generator, shared memory blocks provide interfaces that implement such buffers.
A question that quickly comes to mind is why not use standard FIFO or memory blocks?
The buffers required for hardware co-simulation differ from traditional FIFOs and
memories in that they must be controllable by both the PC and FPGA user design logic.
The standard FIFO and memory blocks provided by System Generator can only interface
with user design logic.
There are two types of shared memories that provide this control: lockable shared
memories and shared FIFOs. These blocks provide different buffering styles; each with
their own handshaking protocols that determine when and how burst transactions with
the FPGA occur. In this tutorial, primary attention is focused on shared FIFO buffers. For
an example on how to use lockable shared memories, please refer to the tutorial entitled
Real-Time Signal Processing using Hardware Co-Simulation. You may find the lockable
shared memory and FIFO blocks in the Shared Memory library of the Xilinx Blockset.
Because shared FIFOs play a central role in enabling vector transfers, it is worth a brief
aside to discuss their behavior. A shared FIFO pair is comprised of a To FIFO block and a
From FIFO block that specify the same name (e.g., Bar in the figure above). The To FIFO
block provides the "write side" control signals, while the From FIFO block provides the
"read side" control signals. When used together, a shared FIFO pair is conceptually the
same thing as a single FIFO – only the control signals for the two sides are graphically
disjoint. This means that a shared FIFO pair shares the same FIFO memory space. For
example, if you write data into a To FIFO block, you may retrieve the same data by reading
from the From FIFO block. The connection between these two blocks is implicit; shared
FIFOs are associated with one another by name and not by explicit Simulink wires.
Shared FIFOs and shared memories in general may be compiled for hardware cosimulation. Note that although this tutorial touches briefly on how shared FIFOs are cosimulated, it is useful to refer to the topic titled Co-Simulating Shared FIFOs for more indepth information. When one-half of a shared FIFO block is compiled for hardware cosimulation, a full FIFO block is embedded in the FPGA using the FIFO Generator core. One
side of the FIFO connects to user design logic (i.e., the System Generator logic that
connected to the shared FIFO block). The other half connects to interface logic that allows
it to be controlled by the PC. This side of the FIFO may be controlled by other System
Generator software model logic (e.g., the half of the shared FIFO), by a C program or
software executable, or by a MATLAB program. By compiling shared FIFOs for hardware
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co-simulation, you create embedded FIFO-style buffers in the FPGA that can be controlled
directly by a PC.
There are several ways to communicate with a shared FIFO that is embedded inside the
FPGA. The most common approach is to include the other half of the shared FIFO in the
System Generator design. It is also possible to communicate with the shared FIFO using a
C program or MATLAB program. System Generator provides additional blocks that
support vector transfers to and from the FIFO. These blocks will be touched on later in the
tutorial as they play a key role in supporting burst transfers to and from the FPGA.
Adding Buffers to a Design
Having gained an understanding of how shared FIFOs work in hardware, you will now
turn you attention towards building designs that can utilize these buffers for high-speed
vector processing in the FPGA.
Consider the scenario in which you have an FPGA data path that you would like to
accelerate using vector transfers. You need to include input buffer storage in the FPGA that
can store data input samples that are written by the PC. An output buffer is also required
so that the processed data values can be stored while the FPGA waits for the PC to retrieve
them. With these requirements in mind, a From FIFO block is used to implement the input
data buffer and a To FIFO block is used to implement the output data buffer. In the model
shown below, data is written into the data path as soon as it shows up in the input FIFO.
Note that the data path block contains new data (nd) and data valid (vld) flow control
ports. These ports support a simple flow control scheme that determines when new data
enters and valid data leaves the data path. The nd signal is asserted whenever there is data
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available in the input FIFO. Conversely, data is written into the output FIFO whenever
valid data is present on the data path.
To gain a better understanding of how the Shared FIFOs are used, you will now take a look
at an example design that uses vector transfers to accelerate a MAC filter design.
1.
From the MATLAB console, change directory to
<sysgen_tree>/examples/shared_memory/hardware_cosim/frame_acc.
2.
Open macfir_sw_w_fifos.mdl from the MATLAB console.
The example design implements a 32-tap MAC FIR filter that removes additive white noise
from a sinusoid input source. The amount of white noise can be adjusted interactively by
moving the Slider Gain control bar before or during simulation. An output scope compares
the filtered output data against the unfiltered input data. The MAC filter itself is contained
inside a subsystem named hw_cosim. This subsystem contains all of the logic that will be
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compiled into the FPGA for hardware co-simulation. You consider everything else in the
design (i.e., all blocks in the top-level) as the design testbench.
Pushing into the hw_cosim subsystem, you have an n-tap MAC FIR Filter block that
implements the design data path. Wrapping the filter are From FIFO and To FIFO blocks
that provide the input and output buffers, respectively. The MAC filter in the example
design is a modified version of the n-tap MAC filter available in the System Generator DSP
Reference Blockset library. In the example, the filter is modified to include valid in and
valid out ports in order to support the FIFO flow control scheme.
In total, there are four shared memory blocks in the design that define the CA and VA
shared FIFO pairs. In truth, you only need the shared FIFO blocks contained inside the
hw_cosim subsystem to successfully compile the design for hardware co-simulation.
Because you would like to simulate the complete design, including FPGA hardware, you
include a CA To FIFO block and VA From FIFO block in the testbench logic. These shared
FIFO blocks are responsible for writing and reading test data from the shared FIFOs in the
hw_cosim subsystem.
Unfiltered data from the din Gateway In block is written into the CA To FIFO block. At this
point, the CA From FIFO block in the hw_cosim subsystem reads data from the FIFO and
writes it into the MAC filter. The MAC filter in turn processes the data and writes it into the
output buffer, represented by the VA To FIFO block. Lastly, the VA From FIFO block in the
top-level reads the data and sends it to the Scope block for visualization.
For this example, you have chosen a maximum buffer size of 4K. This parameter is set by
specifying 4K for the Depth parameter on the CA From FIFO and VA To FIFO block dialog
boxes. Note that because shared FIFOs are implemented using asynchronous FIFO
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Generator cores, the actual depth of the hardware FIFO is n-1 words, where n is the depth
specified on the dialog box.
You will now have a chance to simulate the design to see how fast it runs in software.
3.
Press the Simulink Start button to simulate the design in software.
4.
Record the time required to simulate the design for 10000 cycles. To get an accurate
measurement, it is preferable to leave the scope block closed since the graphic updates
may affect simulation performance.
You may adjust the Slider Gain bar during simulation to see how the presence of additional
noise affects the filter performance. You may view the filtered and unfiltered data in the
output scope block. The top axis shows the unfiltered input data. The bottom axis shows
the filtered data results.
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Compiling for Hardware Co-simulation
You will now compile the design for hardware co-simulation. Before performing the
following steps, ensure that you have an appropriate hardware co-simulation platform
installed in System Generator and attached to your PC. In this example, you only want to
compile the portion of the design that resides inside the hw_cosim subsystem. This is
because you want the CA To FIFO and VA From FIFO blocks to remain in software as part
of the design testbench (while their partner shared FIFOs are compiled into FPGA logic).
5.
Double-click on the System Generator block in the hw_cosim subsystem to open the
System Generator dialog box.
6.
From the Compilation submenu, choose an appropriate hardware co-simulation
target. Note that although you use the Point-to-point Ethernet hardware co-simulation
interface in this example, any installed hardware co-simulation platform (e.g., a board
that supports JTAG co-simulation) will suffice.
7.
Press the Generate button on the System Generator dialog box to generate the design.
A new hardware co-simulation library and block are created once System Generator
finishes compiling the design. Note that the new hardware co-simulation block does not
have any input or output ports. This is because the subsystem that was compiled did not
contain gateway blocks or Simulink ports. Instead, all connections to other Simulink blocks
are handled implicitly through shared memories that were compiled into the FPGA.
Because you left the To FIFO and From FIFO blocks as part of the software testbench, the
software FIFOs will automatically attach to the FIFOs in hardware at the beginning of
simulation.
It is often necessary to examine the type and configuration of a shared memory that was
compiled for hardware co-simulation. The information about each shared memory is
available in a Shared Memories tab on the hardware co-simulation block dialog box. This
tab contains a tree view of information about each shared memory embedded in the
design.
8.
Double-click on the hardware co-simulation block to open the parameters dialog box.
9.
Select the Shared Memories tab in the hardware co-simulation block dialog box.
The tree-view contains information about the CA and VA shared FIFO blocks that were
compiled. If your co-simulation design contains other shared memory blocks, information
about these blocks will also be displayed here. You may expand or collapse shared
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memory information by clicking on the (+) or (-) icons located adjacent to the shared
memory icons.
10. Close the parameters dialog box.
You are now ready to insert the hardware co-simulation block in the original design. Before
continuing on with the next steps, it is worthwhile to either rename the design or create a
backup of the original since you will be making modifications.
11. Remove the hw_cosim subsystem from the design.
12. Insert the hardware co-simulation block in place of the hw_cosim subsystem.
13. Configure the hardware co-simulation block with any settings necessary to cosimulate using single-step clock mode.
14. Press the Simulink Start button to start the design.
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15. Record the amount of time required to simulate the design for 10000 cycles.
16. Close the design, but leave the hardware co-simulation library open since you will
need it in the next topic.
In the simulation above, hardware co-simulation uses single word transfers. That is,
whenever there is a new simulation value to be read or written to the hardware cosimulation, the PC initiates a transaction with the FPGA. The next topic describes how
vector transfers may be used to increase simulation speed by making more efficient use of
the available hardware co-simulation bandwidth.
Using Vector Transfers
The System Generate Shared Memory Read and Write blocks allow you to use vector
transfers with hardware co-simulation. These blocks may be found in the Shared Memory
library in the Xilinx Blockset.
The Shared Memory Write block accepts a Simulink scalar, vector, matrix or frame data
type and writes the data sequentially into a shared memory. The complete contents of the
Simulink signal are written into the shared memory in a single simulation cycle. As is the
case with all shared memory blocks, an association is made between a Shared Memory
Read or Write block and another shared memory by specifying the same shared memory
name.
Matrix types are treated as having a column-major order. That is, when data is written
sequentially into a shared memory, the elements in a column are written first before
advancing to the next column. For example, assume you have the matrix of data shown
below. During simulation, this matrix data is written into the FIFO (or shared memory) in
the following order:
Using these blocks, it is possible to read or write full vector, frame, or matrix signals into
shared memories, provided the following conditions are met:
•
The input signal driven to a shared memory write block is an 8-bit, 16-bit, or 32-bit
signed or unsigned integer;
•
The number of elements in the vector or matrix does not exceed the depth of the
shared memory or FIFO.
•
The data width of the Shared Memory Read or Write block (i.e., the bitwidth of the
scalar, or vector or matrix element) equals the shared memory or FIFO data width.
You can use these blocks in the example design to read and write vectors of data samples
to the MAC filter in a single software / hardware transaction.
17. Open macfir_hw_w_frames_tb.mdl from the MATLAB console.
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This design is a very similar to the previous design, with a few modifications made to
support the Shared Memory Read and Write blocks. Before simulating the design, you
consider each of these modifications. Most importantly, Shared Memory Read and Write
blocks have been substituted in place of the To and From FIFO testbench blocks in the
previous design. By specifying CA and VA as the Write and Read shared memory names,
respectively, an association is automatically made to the input and output FIFO buffers in
the FPGA hardware during simulation.
A Simulink Buffer block builds a frame of scalar input samples by sequentially buffering
the unfiltered input data. A simple analogy is that the Buffer block is performing a serial to
parallel conversion. Recalling that you compiled the FIFO buffers with a depth of 4K, you
choose a frame size of 4095.
Note that the buffer block introduces a sample rate change in the design. For every 4095
inputs, there is only one output. Thus if the data input sample period is 1, the buffer data
output sample period is 4095. This means that the Shared Memory Write block need only
send a new frame of data to the FPGA on every 4095th simulation cycle (which is
considerably more efficient than initiating a hardware transaction during every simulation
cycle).
Because the Buffer block introduces a rate change, you must adjust the downstream blocks
to accommodate the slower sample period. You begin by telling the Shared Memory Read
block to read a frame of data every 4095th simulation cycle.
18. Double-click on the Shared Memory Read block to open its parameters dialog box.
On the Type field under the Basic tab, you have configured the block to use shared FIFOs.
To ensure a new frame is read at the appropriate time, you configure the Shared Memory
Read block with a Sample time value of 4095.
The Shared Memory Read block allows you to specify the output data type and
dimensions.
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19. On the parameters dialog box, switch to the Output Type tab.
There are several things of interest on this tab. First, you set the output data type as an int32
to match the filter data path output width of 32-bits. Note the design will not simulate
unless these widths match. Secondly, you choose an output dimension that is 4095 words
deep in the Output dimensions field. Finally, you tell the block to generate frame-based
output since frame data types are required by the downstream Unbuffer block.
20. Close the parameters dialog box.
The Simulink Unbuffer block takes the frame data from the Shared Memory Read block
and deserializes it into sequential scalar values. The Simulink Unbuffer block also
introduces a sample rate change in the diagram. Because the input sample period to the
block is 4095, and the frame size is 4095 words, the Unbuffer block output sample period is
1. This works out nicely since you have data moving through the overall system at an
effective sample period of 1.
Because the Shared Memory Write and Read block operate on integer values, you must
insert Simulink type conversion blocks into the diagram so that the data is interpreted
correctly in various portions of the model. The in_data_conv subsystem converts the
Simulink doubles into 16-bit integer values that can be interpreted appropriately by the
FPGA hardware. On the output side, the out_data_conv subsystem converts the 32-bit
integers into 32-bit Simulink fixed-precision values.
Before simulating the design, you must add the hardware co-simulation block you created
from the previous design.
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21. Add the hardware co-simulation block to the design as shown below.
As mentioned before, the Shared Memory Write block writes a new input frame of 4095
words to the FPGA on every 4095th clock cycle. Likewise, the Shared Memory Read block
reads an output frame of 4095 words from the FPGA on every 4095th clock cycle. This
means that the FPGA must process the entire frame in a single-cycle. How exactly is this
accomplished?
The first step is to configure the FPGA in free-running clock mode. In doing so, you allow
the FPGA to process data considerably faster than if it were otherwise kept in lockstep with
the Simulink simulation. Whereas in single-step mode the FPGA can only process one data
per Simulink cycle, the FPGA processing speed is limited only by the system clock
frequency when operating in free-running clock mode. Even so, if the buffer is large
enough, the FPGA may not have time to process the complete buffer before the next block
in the design is woken up. You still need a way to stall the rest of the simulation while the
FPGA processes the entire buffer.
The Shared Memory Read block checks the number of FIFO words available in the output
buffer before trying to read a frame. If the number of words in the buffer is insufficient, the
Read block waits for a small amount of time, and then checks again to determine if the
words have become available. It only reads the frame once all of the words are available in
the output buffer, in this case 4095. In this manner, the Shared Memory Read block can stall
the simulation until the complete frame has been processed by the FPGA.
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The simulation flow of data through the diagram is shown below.
Two steps necessary to run the simulation using Simulink frames signals are provided
below:
22. Double-click on the hardware co-simulation block to bring up the parameters dialog
box.
23. Select Free running clock mode as shown below.
24. Configure the hardware co-simulation block with any additional settings necessary for
simulation according to the requirements of your co-simulation platform.
25. Press the Simulink Start button to start the design.
26. Record the amount of time required to simulate the design for 10000 cycles.
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Real-Time Signal Processing using Hardware Co-Simulation
The shared memory interfaces available in System Generator allow signal processing
designs with high bandwidth and memory requirements to be co-simulated using FPGA
hardware. When used in conjunction with the Xilinx Shared Memory Read and Write
blocks, it is possible for hardware co-simulation designs to process complete Simulink
vector and matrix signals in a single simulation cycle. These large data transactions
between Simulink and the FPGA are realized using burst transfers, and depending on the
co-simulation interface, often provide sufficient throughput for real-time signal processing
applications.
There are two types of System Generator interfaces that support burst transfers when
compiled into FPGA hardware. These interfaces include lockable shared memories and
shared FIFO blocks. Both blocks provide different handshaking protocols that determine
how and when transactions between the FPGA and host PC occur. Before using these
blocks, it is useful to understand how they work in relation to hardware co-simulation. For
more information, please refer to the following topics:
Co-Simulating Lockable Shared Memories
Co-Simulating Shared FIFOs
In this document, a high-speed co-simulation buffering interface implemented as a System
Generator model is presented. The example interface uses lockable-shared memories to
implement the required buffer storage. Note that it is relatively straightforward to modify
the flow control logic so that shared FIFOs may be used in place of the shared memories.
The high-speed buffering interface is discussed first, followed by an example in which the
interface is used to support real-time processing of a video stream using a 5x5 filter kernel.
Described last is how an additional unprotected shared memory is applied to the system to
support dynamic reloading of the image kernel during co-simulation.
Shared Memory I/O Buffering Example
When a lockable shared memory is compiled for hardware co-simulation, additional
circuitry is included in the FPGA to the handle the mutual exclusion. Part of this circuitry
includes logic to enable high-speed transfers of the memory image when the FPGA
acquires or releases lock of the memory. It takes advantage of the lockable shared memory
mutual exclusion semantics to implement a high-speed I/O buffering interface for
hardware co-simulation. This topic describes this interface, which is included as an
example model in your System Generator software installation.
1.
From the MATLAB console, change directory to
<sysgen_tree>/examples/shared_memory/hardware_cosim/io_bufferin
2.
Open highspeed_iobuf_ex.mdl from the MATLAB console.
The I/O buffering interface allows you to easily buffer and stream data through a System
Generator signal processing data path during hardware co-simulation. The example
design is comprised of two subsystems that implement input and output buffer storage,
named Input Buffer and Output Buffer, respectively. The turquoise block in the center of
the diagram is a placeholder for the signal processing data path which you will substitute
into the design.
At the heart of each buffering subsystem is a lockable shared memory block that provides
the buffer storage. Each shared memory is wrapped by logic that controls the flow of data
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from the host PC, through the interface, and back to the host PC. Operation of the I/O
buffering interface is shown in the flow chart below:
Notice that the buffering interface design includes several data valid ports. These ports are
used for data flow control. A "true" output from the Input Buffer dout_valid port
indicates new data is ready to be processed by the data path. Likewise, when the data path
is finished processing the data, it should drive the Output Buffer subsystem's
din_valid port to "true" to indicate valid output data (the din_valid port is analogous to
a write enable control signal).
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The example includes a placeholder that should be replaced by a System Generator data
path. You may insert any data path in the buffer interface provided that it works within the
valid signal semantics described above.
Note: The output buffer shared memory does not release lock until the output buffer is full. To avoid
deadlock, the number of valid assertions by the data path should equal the output memory buffer size
for a given processing cycle.
Applying a 5x5 Filter Kernel Data Path
You will now apply a data path to the I/O buffering interface to demonstrate a complete
system capable of processing a 128x128 8-bit grayscale video stream in real-time. You have
chosen to use a 5x5 image processing kernel to implement the data path portion of the
high-speed buffering interface. For more information about the filter kernel, refer to the
System Generator demo entitled sysgenConv5x5. You begin by considering various
aspects of the design implementation.
3.
From the MATLAB console, change directory to
$SYSGEN/examples/shared_memory/hardware_cosim/conv5x5_video.
4.
Open conv5x5_video_ex.mdl from the MATLAB console.
Buffer and Data Path Configuration
With the frame and pixel constraints in mind, the input and output buffer parameter
dialog boxes are configured with a depth of 128x128 (16K) words and a word width of 8bits. This depth allows the interface to process a complete frame in a single simulation
cycle. Note that these configuration parameters are propagated automatically to the
lockable shared memories that implement the buffer storage.
The data path uses line buffers to properly align data samples in the filter kernel. The size
of these line buffers can be parameterized to accommodate different frame sizes. In this
example, the line buffers are implemented in the Virtex2 5 Line Buffer block in the
conv5x5_video_ex/5x5_filter subsystem, and are pre-configured with a line size of
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128. If you decide to process a different size frame, the Line Size parameter should be
updated accordingly.
Valid Bit Generation
The data path includes a subsystem named valid_generator that is responsible for
driving the din_valid port of the output buffer block. The subsystem has two inputs,
valid_in and offset. The valid_in port is driven by the dout_valid signal from the
input buffer block, which is delayed by a variable number of cycles before it is driven to the
valid_out port. The logic associated with the valid_generator subsystem is shown
below.
An addressable shift register block (ASR) is used to delay the valid bit. The offset port is
used to control the address of the ASR block, which in turn controls the amount of latency
the valid bit incurs. By simply delaying the valid bit generated by the input buffer block,
You ensure the number of words written to the output buffer is always equal to the buffer
size. Note that when the design is run in hardware, a change in the offset value will cause
the vertical alignment of the filtered images to change.
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Support for Coefficient Reloading
An interesting characteristic of the kernel data path is that its coefficients can be
dynamically reloaded at run-time. The 5x5 filter block includes Load and Coef control
ports, which are driven by the coefficient_memory subsystem.
The coefficient_memory contains a copy of the most recently loaded filter coefficients,
which are stored in an unprotected shared memory named coef_buffer. During runtime, the subsystem monitors the shared memory contents, and initiates a reload sequence
if detects a change. By co-simulating the unprotected shared memory, any process on the
host PC may write new kernel coefficients simply by writing to a shared memory object
named coef_buffer. This interface is convenient, as communication with the FPGA
hardware is completely abstracted through the Shared Memory API.
Compiling for Hardware Co-simulation
The full filter kernel design must be compiled for hardware co-simulation before it can be
simulated.
5.
Double click on the System Generator block located at the top of the
conv5x5_video_ex model.
6.
Select an appropriate hardware co-simulation target.
7.
Press the Generate button to compile the design for hardware co-simulation.
A hardware co-simulation block is created once the design finishes compiling.
Hardware co-simulation blocks include information about any shared memories, registers,
or FIFOs that were compiled as part of the design. You may view this information by
double-clicking on the hardware co-simulation block to open the parameters dialog box.
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Once the dialog box is open, selecting the Shared Memories tab reveals information
about each shared memory in the compiled design.
Go ahead and leave the hardware co-simulation library open. In the next topic you will
include the hardware co-simulation block in a video processing testbench design.
5x5 Filter Kernel Test Bench
Included with the example files is a Simulink test bench model that uses the hardware cosimulation block to filter a looped video sequence.
8.
From the
$SYGEN/examples/shared_memory/hardware_cosim/conv5x5_video
directory, open conv5x5_video_testbench.mdl.
The testbench model uses a From Workspace block to produce the looped video sequence.
Each frame of the video sequence is represented as a 128x128 uint8 Simulink matrix (a
pre-load function loads and initializes the video sequence automatically when the model is
opened). Video frames are written into the FPGA Processing subsystem where they are
filtered at the rate of one frame per simulation cycle. The filtered output is then written to
a Matrix Viewer block for analysis.
The FPGA Processing subsystem contains a stub for the hardware co-simulation block,
as well as Shared Memory Read and Write blocks. In this example, the Shared Memory
Read and Write blocks are responsible for managing video frame I/O to and from the
shared memories operating inside the FPGA. The operation of these blocks is described
below:
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The Shared Memory Write block wakes up and requests lock of the input buffer
lockable shared memory Foo. Once lock is granted, the block writes the video
frame data input into the lockable shared memory and releases lock.
b.
The hardware co-simulation block wakes up and requests lock of the input and
output buffer shared memories Foo and Bar. The host PC shared memory images
are transferred to the FPGA and lock is granted. The FPGA processes the input
buffer data and writes the output into the output buffer. Lastly the FPGA releases
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lock of Foo and Bar, causing the FPGA shared memory images to be transferred
back to the host PC.
c.
The Shared Memory Read block wakes up and requests lock of the output buffer
lockable shared memory Bar. The block reads a video from the output buffer and
drives its output port with the processed video frame data.
Note that the three steps listed above assume a specific sequencing of the hardware cosimulation and Shared Memory Read and Write blocks. To ensure these blocks are
properly sequenced, you can set block priorities, where a lower priority block is woken up
first during simulation.
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9.
Add the hardware co-simulation block to the testbench model in place of the turquoise
placeholder residing in the FPGA Processing subsystem.
The Shared Memory Write block in the testbench is pre-configured with a priority of 1, and
the Shared Memory Read block is pre-configured with a priority of 3. Since you want the
hardware co-simulation block to wake up second in the simulation sequence, you must set
the hardware co-simulation block priority to 2.
10. Right-click on the hardware co-simulation block, and select Block Properties.
11. Specify a Priority of 2 in the Block Properties dialog box.
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For high-speed processing applications, the hardware co-simulation block should be
configured to operate in Free Running clock mode. When this mode is used, the
synchronization between the FPGA and Simulink are handled entirely by the lockable
shared memories. By running the FPGA in free-running mode, you allow it to run fast
enough to process a complete video frame in a single Simulink cycle. Keep in mind that the
hardware co-simulation block circuitry waits to acquire lock before processing data. Since
the lock cannot be granted until the hardware co-simulation block is woken up, the FPGA
sits idle until new data is presented in the input buffer.
12. Double-click on the hardware co-simulation block and choose a Free Running
Clock under the Basic Tab.
You are now ready to simulate the design.
13. Press the Simulink Start button to start simulation.
Two windows will appear showing the original and filtered video streams.
The left image is the original video frame. The image on the right is the same frame that has
been processed using the "smooth" filter kernel. Note that the smoothing filter is just one of
several filters that can be applied to the video source.
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Reloading the Kernel
The filter data path is designed so that the filter kernel can be reloaded dynamically while
hardware co-simulation is running. Once the simulation is running, you may use the
xlReloadFilterCoef function to load a new kernel. The function accepts a string kernel
identifier (e.g., sobelxy) as an input parameter. A list of available filter kernels can be
viewed by typing help xlReloadFilterCoef in the MATLAB console. The function is
supplied as a MATLAB source file and can be found in the
$SYGEN/examples/shared_memory/hardware_cosim/conv5x5_video
directory.
Note: Once you have reloaded the filter, you may choose to adjust the coefficient gain. The gain can
be adjusted using the Coefficient Adjust slider control at the top-level of the testbench model. This
also demonstrates how System Generator's traditional, port-based, hardware co-simulation
interfacing can be used in conjunction with the shared memory hardware co-simulation interfaces.
It is worthwhile to note that System Generator provides a MATLAB object interface to
shared memory objects. The xlReloadFilterCoef function uses this object interface to
write new coefficients into the unprotected shared memory named coef_buffer running in
the FPGA. The function is fully annotated with comments that explain how the shared
memory object is created, written to, and released when the operation is complete.
Note: The source code for the MATLAB object interface is supplied with the System Generator
software installation, and can be found in the $SYGEN/examples/shared_memory/mex_function
directory. Also included in this directory is MATLAB M-code that demonstrates how the mex-function
source code was built.
14. After ensuring the testbench design is running, load the SobelXY filter kernel into the
FPGA by typing xlReloadFilterCoef('sobelxy') from the MATLAB command
window.
You will now see the video output generated using the SobelX-Y kernel.
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Installing Your Hardware Co-Simulation Board
Installing an ML402 Board for Ethernet Hardware Co-Simulation
The following procedure describes how to install and configure the hardware and software
required to run Ethernet Hardware Co-Simulation on an ML402 board.
Assemble the Required Hardware
1.
Xilinx Virtex-4 SX ML402 Platform which includes the following:
a.
Virtex-4 ML402 board
b. 5V Power Supply bundled with the ML402 Kit
c.
2.
CompactFlash Card
You also need the following items on hand:
a.
Ethernet network Interface Card (NIC) for the host PC.
b.
Ethernet RJ45 Male/Male cable. (May be a Network or Crossover cable.)
c.
CompactFlash Reader for the PC.
Install the Software on the Host PC
Make sure the following software is installed on your PC:
•
System Generator version as specified in the current System Generator Release Notes
•
Xilinx ISE Software version as specified in the current System Generator Release
Notes
•
WinPcap version 4.0, which may be installed through the System Generator installer
or obtained from the website at http://www.winpcap.org.
Setup the Local Area Network on the PC
You are required to have a 10/100 Fast Ethernet or a Gigabit Ethernet Adapter on you PC.
To configure the settings do the following:
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1.
As shown below, from the Start menu, select Control Panel, then right-click on Local
Area Connection, then select Properties.
2.
As shown below, select Internet Protocol (TCP/IP), then click on the Properties button
and set the IP Address 192.168.8.2 and Subnet mask to 255.255.255.0. (The last digit of
the IP Address must be something other than 1, because 192.168.8.1 is the default IP
address for the ML402. See the topic Load the Sysgen ML402 HW Co-Sim
Configuration Files below for further details.)
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3.
Click on the Configure button, select the Advanced tab, select Flow Control, then
select Auto.
4.
Set Speed & Duplex to Auto, then click out using the OK button.
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Load the Sysgen ML402 HW Co-Sim Configuration Files
System Generator comes with HW Co-Sim configuration files that first need to be loaded
into the ML402 CompactFlash card with a CompactFlash Reader.
1.
Optionally Backup the ML402 Demo Files
The ML402 CompactFlash card comes with a series of demo files that you might want to
re-load and exercise later.
a.
Connect the CompactFlash Reader to the PC. This is usually done through a USB
port.
b.
Insert the CompactFlash card into a CompactFlash Reader.
c.
Click on the MyComputer icon, then select the Removable Disk drive that
represents the CompactFlash Reader.
d. Create or open a backup folder on the PC and copy the content of the
CompactFlash card to that folder for later use.
Note: For the following steps, 'e:' is assumed to be the drive name associated with the
CompactFlash reader.
2.
Re-Format the CompactFlash Card
The card needs to be re-formatted to a FAT16 file system before the System Generator files
can be transferred. You use the mkdosfs utility to format the card.
a.
Download the mkdosfs program from the Xilinx URL address:
http://www.xilinx.com/products/boards/ml310/current/utilities/mkdosfs.zip.
b.
Extract to folder C:/mkdosfs
c.
Open a Windows shell by selecting Start > Run..., then type cmd in the Run dialog
box and click OK.
d. In the shell, move to the mkdosfs folder:
cd C:\mkdosfs
Caution! In the following step, make sure the drive name (e.g., 'e:' in this case) is specified
correctly for the Compact Flash Removable Disk. Otherwise, the information on the mistakenly
targeted drive will be erased and the drive will be re-formatted.
e.
Type the following mkdosfs command after the Windows command prompt:
mkdosfs -v -F 16 e:
The content of the Compact Flash card should be wiped clean and re-formatted.
3.
Copy the Sysgen configuration files to the Compact Flash card
Note: For reference, the Sysgen files to be copied are located at the following pathname:
...<sysgen_tree>\plugins\bin\ML402_sysace_cf.zip
Invoke MATLAB on the PC, then enter the following command on the MATLAB
Command Line:
unzip(fullfile(xlFindSysgenRoot,'plugins/bin/ML402_sysace_cf.zip'),'e:/')
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The following files and folder should now be listed on the CompactFlash drive:
Optional Step to set the Ethernet MAC Address and the IPv4 Address
Note: The following step may be necessary if the default MAC and IP addresses conflict with your
default network settings, or if you wish to co-simulate two or more ML402 boards concurrently. If not,
proceed to the next topic.
After writing the data to the card, you will find two files, mac.dat and ip.dat, in the
card root directory. The mac.dat and ip.dat files specify the Ethernet MAC address
and IPv4 address associated with the board, respectively. These addresses are used to
uniquely identify a target board during Ethernet hardware co-simulation.
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a.
Open mac.dat in a text editor and change the Ethernet MAC address. The MAC
address must be specified as a six pair of two-digit hexadecimal separated by
colons (e.g. 00:0a:35:11:22:33). All-zeros, broadcast, or multicast MAC
addresses are not supported.
b.
Open ip.dat in a text editor and change the IP address. The IP address must be
specified in IPv4 dotted decimal notation (e.g. 192.168.8.1). All-zeros,
broadcast, multicast, or loop-back IP address are not supported. After changing
the IP address for ML402 board, update the IP address for the network connection
on the PC accordingly as mentioned in topic Setup the Local Area Network on the
PC. For direct connection, the ML402 and the PC must be on the same subnet.
Otherwise, the ML402 IP address should be reachable from the PC and vice versa.
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Setup the ML402 Board
The figure below illustrates the ML402 components of interest in this setup procedure:
1.
Position the ML402 board so the Virtex™-4 and Xilinx logos are oriented near the top
edge of the board.
2.
Make sure the power switch, located in the upper-right corner of the board, is in the
OFF position.
3.
As shown below, Eject the CompactFlash card from the CompactFlash Reader.
4.
Remove the CompactFlash card from the CompactFlash Reader.
5.
Locate the CompactFlash card slot (on the back side of the ML402 board), and carefully
insert the CompactFlash card with its front label facing away from the board. The
figure below shows the back side of the board with the ConpactFlash card properly
inserted.
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Note: The CompactFlash card provided with your board might differ.
Caution! Be careful when inserting or removing the CompactFlash card from the slot. Do not
force it.
6.
Connect the AC power cord to the power supply brick. Plug the power supply adapter
cable into the ML402 board. Plug in the power supply to AC power.
Caution! Make sure you use an appropriate power supply with corrrect voltage and power
ratings.
7.
Using the RJ45 Male/Male Ethernet Cable, connect the Ethernet connector on the
ML402 board directly to the Ethernet connector on the host PC.
8.
Set the Configuration Address DIP Switches.
As shown below, set the Configuration Address DIP Switches as follows: 1:on, 2:off,
3:off, 4:on, 5:off, 6:on]
9.
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Set the Configuration Source Selector Switch.
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As shown below, set the Configuration Source Selector Switch to SYS ACE
10. Verify the Configuration Settings
a.
Turn the target board Power switch ON.
b.
Check the on-board status LEDs to ensure the FPGA is configured. If the
configuration succeeded, the DONE LED should be on and all error LEDs should
be off.
c.
As shown below, check the information displayed on the 16-character 2-line LCD
screen of the board. If no error occurred, the Ethernet MAC address (without
colons) should appear on the first line of the display and the IPv4 address should
appear on the second line.
d. If the LCD display does not show the information correctly, press the System ACE
Reset button to reconfigure the FPGA.
e.
Check the status LEDs again to ensure the configuration sequence completed
successfully.
11. Verify the Ethernet Interface and Connection Status
System Generator for DSP
Release 10.1.1 April, 2008
a.
Connect the Ethernet interface of the board to a network connection, or directly to
a host.
b.
Check the on-board Ethernet status LEDs to make sure the Ethernet interface is
attached to an active Ethernet segment. The LEDs should reflect the link speed and
the duplex mode at which the interface is operating. The TX and RX leds should
flash on and off occasionally depending on the network traffic. If no LED is on,
press the CPU Reset button to reset the FPGA, and also examine whether the
Ethernet segment is active.
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c.
To ensure the board is reachable by the host, issue ICMP ping from the host to
check the connectivity. For example, type "ping 192.168.8.1" on a console to test the
connectivity to a board with IP address 192.168.8.1.
d. The target FPGA listens on the UDP port 9999. Please ensure the underlying
network does not block the associated traffic when network-based Ethernet
configuration is used. This does not affect point-to-point Ethernet configuration.
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Installing an ML506 Board for Ethernet Hardware Co-Simulation
The following procedure describes how to install and configure the hardware and software
required to run an ML506 Board Point-to-Point Ethernet Hardware Co-Simulation.
Assemble the Required Hardware
1.
2.
Xilinx Virtex-5 SX ML506 Platform which includes the following:
a.
Virtex-5 ML506 board
b.
5V Power Supply bundled with the ML506 kit
c.
CompactFlash Card
You also need the following items on hand:
a.
Ethernet network Interface Card (NIC) for the host PC.
b.
Ethernet RJ45 Male/Male cable. (May be a Network or Crossover cable.)
c.
CompactFlash Reader for the PC.
Install the Software on the Host PC
Make sure the following software is installed on your PC:
•
System Generator version as specified in the current System Generator Release Notes.
•
Xilinx ISE Software version as specified in the current System Generator Release
Notes.
•
WinPcap version 4.0, which may be installed through the System Generator installer
or obtained from the website at http://www.winpcap.org.
Setup the Local Area Network on the PC
You are required to have a 10/100 Fast Ethernet or a Gigabit Ethernet Adapter on you PC.
To configure the settings do the following:
1.
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Release 10.1.1 April, 2008
As shown below, from the Start menu, select Control Panel, then right-click on Local
Area Connection, then select Properties.
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2.
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As shown below, select Internet Protocol (TCP/IP), then click on the Properties button
and set the IP address 192.168.8.2 and the Subnet mask to 255.255.255.0. (The last digit
of the IP Address must be something other than 1 because 192,168.8.1 is the default IP
address fo ML506. See Load the Sysgen ML506 HW Co-Sim Configuration Files for
further details.).
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3.
Click on the Configure button, select the Advanced tab, select Flow Control, then
select Auto.
4.
Set Speed & Duplex to Auto, then click out using the OK button.
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Load the Sysgen ML506 HW Co-Sim Configuration Files
System Generator comes with HW Co-Sim configuration files that first need to be loaded
into the ML506 CompactFlash card with a CompactFlash Reader.
1.
Optionally Backup the ML506 Demo Files
The ML506 CompactFlash card comes with a series of demo files that you might want to
re-load and exercise later.
a.
Connect the CompactFlash Reader to the PC. This is usually done through a USB
port.
b.
Insert the CompactFlash card into a CompactFlash Reader.
c.
Click on the MyComputer icon, then select the Removable Disk drive that
represents the CompactFlash Reader..
d. Create or open a backup folder on the PC and copy the content of the
CompactFlash card to that folder for later use.
Note: For the following steps, 'e:' is assumed to be the drive name associated with the
CompactFlash reader.
2.
Re-Format the CompactFlash Card
The card needs to be re-formatted to a FAT16 file system before the System Generator files
can be transferred. You use the mkdosfs utility to format the card.
a.
Download the mkdosfs program from the Xilinx URL address:
http://www.xilinx.com/products/boards/ml310/current/utilities/mkdosfs.zip.
b.
Extract to folder C:/mkdosfs
c.
Open a Windows shell by selecting Start > Run..., then type cmd in the Run dialog
box and click OK.
d. In the shell, move to the mkdosfs folder:
cd C:\mkdosfs
Caution! In the following step, make sure the drive name (e.g., 'e:' in this case) is specified
correctly for the Compact Flash Removable Disk. Otherwise, the information on the mistakenly
targeted drive will be erased and the drive will be re-formatted.
e.
Type the following mkdosfs command after the Windows command prompt:
mkdosfs -v -F 16 e:
The content of the Compact Flash card should be wiped clean and re-formatted.
3.
Copy the Sysgen configuration files to the Compact Flash card
Note: For reference, the Sysgen files to be copied are located at the following pathname:
...<sysgen_tree>\plugins\bin\ML506_sysace_cf.zip
Invoke MATLAB on the PC, then enter the following command on the MATLAB
Command Line:
unzip(fullfile(xlFindSysgenRoot,'plugins/bin/ML506_sysace_cf.zip'),'e:/')
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The following files and folder should now be listed on the CompactFlash drive:
Optional Step to set the Ethernet MAC Address and the IPv4 Address
Note: The following step may be necessary if the default MAC and IP addresses conflict with your
default network settings, or if you wish to co-simulate two or more ML506 boards concurrently. If not,
proceed to the next topic.
After writing the data to the card, you will find two files, mac.dat and ip.dat, in the
card root directory. The mac.dat and ip.dat files specify the Ethernet MAC address
and IPv4 address associated with the board, respectively. These addresses are used to
uniquely identify a target board during Ethernet hardware co-simulation.
System Generator for DSP
Release 10.1.1 April, 2008
a.
Open mac.dat in a text editor and change the Ethernet MAC address. The MAC
address must be specified as a six pair of two-digit hexadecimal separated by
colons (e.g. 00:0a:35:11:22:33). All-zeros, broadcast, or multicast MAC
addresses are not supported.
a.
Open ip.dat in a text editor and change the IP address. The IP address must be
specified in IPv4 dotted decimal notation (e.g. 192.168.8.1). All-zeros,
broadcast, multicast, or loop-back IP address are not supported. After changing
the IP address for the ML506 board, update the IP address for the network
connection on the PC accordingly as mentioned in the topic Setup the Local Area
Network on the PC. For direct connection, the ML506 and the PC must be on the
same subnet. Otherwise, the ML506 IP address should be reachable from the PC
and vice versa.
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Setup the ML506 Board
The figure below illustrates the ML506 components of interest in this setup procedure:
Configuration Address
DIP Switches (SW3)
Power Connector
Power Switch
Ethernet
Ethernet Mode Select
jumpers (J22 & J23)
238
Ethernet Status LEDs
LCD
1.
Position the ML506 board so the Xilinx logo is oriented near the lower-left corner.
2.
Make sure the power switch, located in the upper-right corner of the board, is in the
OFF position.
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3.
As shown below, Eject the CompactFlash card from the CompactFlash Reader.
4.
Remove the CompactFlash card from the CompactFlash Reader.
5.
Locate the CompactFlash card slot (on the back side of the ML506 board), and carefully
insert the CompactFlash card with its front label facing away from the board. The
figure below shows the back side of the board with the ConpactFlash card properly
inserted.
Note: The CompactFlash card provided with your board might differ.
Caution! Be careful when inserting or removing the CompactFlash card from the slot. Do not
force it.
6.
Connect the AC power cord to the power supply brick. Plug the 5V power supply
adapter cable into the ML506 board. Plug in the power supply to AC power.
Caution! Make sure you use an appropriate power supply with correct voltage and power
ratings.
7.
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Using the RJ45 Male/Male Ethernet Cable, connect the Ethernet connector on the
ML506 board directly to the Ethernet connector on the host PC.
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8.
Set the SW3 Configuration Address DIP Switches.
SW3 Configuration
Address
DIP Switches
(not yet configured)
Set the Configuration Address DIP Switches as follows:
1:on, 2:off, 3:off, 4:on, 5:off, 6:on, 7:off, 8:on
9.
Set the Ethernet Mode Select jumpers
As shown below, connect pin 1 and 2 on both the Ethernet Mode Select jumpers (J22
and J23)
Ethernet Mode Select
jumpers (J22 & J23)
10. Verify the Configuration Settings
240
a.
Turn the target board Power switch ON.
b.
Check the on-board status LEDs to ensure the FPGA is configured. If the
configuration succeeded, the DONE LED should be on and all error LEDs should
be off.
c.
As shown below, check the information displayed on the 16-character 2-line LCD
screen of the board. If no error occurred, the Ethernet MAC address (without
colons) should appear on the first line of the display and the IPv4 address should
appear on the second line.
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Installing Your Hardware Co-Simulation Board
d. If the LCD display does not show the information correctly, press the System ACE
Reset button to reconfigure the FPGA.
System ACE Reset
e.
Check the status LEDs again to ensure the configuration sequence completed
successfully.
11. Verify the Ethernet Interface and Connection Status
System Generator for DSP
Release 10.1.1 April, 2008
a.
Connect the Ethernet interface of the board to a network connection, or directly to
a host.
b.
Check the on-board Ethernet status LEDs to make sure the Ethernet interface is
attached to an active Ethernet segment. The LEDs should reflect the link speed and
the duplex mode at which the interface is operating. The TX and RX leds should
flash on and off occasionally depending on the network traffic. If no LED is on,
press the CPU Reset button to reset the FPGA, and also examine whether the
Ethernet segment is active.
c.
To ensure the board is reachable by the host, issue ICMP ping from the host to
check the connectivity. For example, type "ping 192.168.8.1" on a console to test the
connectivity to a board with IP address 192.168.8.1.
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d. The target FPGA listens on the UDP port 9999. Please ensure the underlying
network does not block the associated traffic when network-based Ethernet
configuration is used. This does not affect point-to-point Ethernet configuration.
Installing a Spartan-3A DSP 1800A Starter Platform for Ethernet
Hardware Co-Simulation
The following procedure describes how to install and setup the hardware and software
required to run Hardware Co-Simulation on a Spartan-3A DSP 1800A Starter Platform.
This platform uses a JTAG cable instead of System ACE to download the configurtion
bitstream.
Assemble the Required Hardware
1.
2.
Xilinx Spartan-3A DSP 1800A Starter Platform which includes the following:
a.
Spartan-3A DSP 1800A Starter Platform
b.
5V Power Supply bundled with the development kit
You also need the following items on hand:
a.
Ethernet network Interface Card (NIC) for the host PC.
b.
Ethernet RJ45 Male/Male cable. (May be a Network or Crossover cable.)
c.
Xilinx Parallel Cable IV with associated Power Jack splitter cable or a Xilinx
Platform USB Cable and a 14-pin ribbon cable.
Install the Software on the Host PC
Make sure the following software is installed on your PC:
•
System Generator version as specified in the current System Generator Release Notes.
•
Xilinx ISE Software version as specified in the current System Generator Release
Notes.
•
WinPcap version 4.0, which may be installed through the System Generator installer
or obtained from the website at http://www.winpcap.org.
Setup the Local Area Network on the PC
You are required to have a 10/100 Fast Ethernet or a Gigabit Ethernet Adapter on you PC.
To configure the settings do the following:
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1.
As shown below, from the Start menu, select Control Panel, then right-click on Local
Area Connection, then select Properties.
2.
As shown below, select Internet Protocol (TCP/IP), then click on the Properties button
and set the IP address 192.168.8.2 and the Subnet mask to 255.255.255.0. (The last digit
of the IP Address must be something other than 1 because 192.168.8.1 is the default IP
address for Starter Platform.
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3.
Click on the Configure button, select the Advanced tab, select Flow Control, then
select Auto.
4.
Set Speed & Duplex to Auto, then click out using the OK button.
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Setup the Spartan-3A DSP 1800A Starter Platform
1.
Position the Spartan-3A DSP 1800A Starter Platform so the Xilinx logo is oriented
rightside up and located in the lower-right quadrant of the platform.
2.
Make sure the power switch, located in the upper-right corner of the platform, is in the
OFF position.
3.
If you are using a Xilinx Parallel Cable IV, follow steps 3a through 3d.
a.
Connect the DB25 Plug Connector on the Xilinx Parallel Cable IV to the IEEE-1284
compliant PC Parallel (Printer) Port Connector .
b. Using the narrow (14 pin) 6” High Performance Ribbon cable, connect the pod end
of the Xilinx Parallel Cable IV to the JTAG Port (J2) on the Starter Platform.
c.
Connect the attached Power Jack cable to the Keyboard/Mouse connector on the
PC.
d. If necessary, connect the male end of the Keyboard/Mouse cable to the associated
female connector on the Xilinx Power Jack cable (splitter cable) .
4.
If you are using a Xilinx Platform Cable USB, follow step 4a and 4b.
a.
Connect the Xilinx Platform Cable USB to a USB port on the PC.
b. Using the narrow (14 pin) 6” High Performance Ribbon cable, connect the pod end
of the Xilinx Platform Cable USB to the JTAG Port (J2) on the Starter Platform.
5.
Connect the AC power cord to the power supply brick. Plug the 5V power supply
adapter cable into the 5V DC ONLY connector (J5) on the Starter Board. Plug the power
supply cord into AC power.
Caution! Make sure you use an appropriate power supply with correct voltage and power
ratings.
6.
Turn the Spartan-3A DSP 1800A Starter Platform POWER switch ON.
Installing a Spartan-3A DSP 3400A Development Platform for Ethernet
Hardware Co-Simulation
The following procedure describes how to install and configure the hardware and software
required to run an Spartan-3A DSP 3400A Development Platform Point-to-Point Ethernet
Hardware Co-Simulation.
Assemble the Required Hardware
1.
2.
System Generator for DSP
Release 10.1.1 April, 2008
Xilinx Spartan-3A DSP 3400A Development Platform Kit which includes the
following:
a.
Spartan-3A DSP 3400A Development board
b.
+12V Power Supply bundled with Board LYR178-101C (Rev C) or
+5 V Power Supply bundled with Board LYR178-101D (Rev D)
c.
CompactFlash Card
You also need the following items on hand:
a.
Ethernet network Interface Card (NIC) for the host PC.
b.
Ethernet RJ45 Male/Male cable. (May be a Network or Crossover cable.)
c.
CompactFlash Reader for the PC.
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Install the Software on the Host PC
Make sure the following software is installed on your PC:
•
System Generator version as specified in the current System Generator Release Notes.
•
Xilinx ISE Software version as specified in the current System Generator Release
Notes.
•
WinPcap version 4.0, which may be installed through the System Generator installer
or obtained from the website at http://www.winpcap.org.
Setup the Local Area Network on the PC
You are required to have a 10/100 Fast Ethernet or a Gigabit Ethernet Adapter on you PC.
To configure the settings do the following:
246
1.
As shown below, from the Start menu, select Control Panel, then right-click on Local
Area Connection, then select Properties.
2.
As shown below, select Internet Protocol (TCP/IP), then click on the Properties button
and set the IP address 192.168.8.2 and the Subnet mask to 255.255.255.0. (The last digit
of the IP Address must be something other than 1 because 192,168.8.1 is the default IP
address fo ML506. See Load the Sysgen ML506 HW Co-Sim Configuration Files for
further details.).
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3.
Click on the Configure button, select the Advanced tab, select Flow Control, then
select Auto.
4.
Set Speed & Duplex to Auto, then click out using the OK button.
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Release 10.1.1 April, 2008
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Load the Sysgen Spartan-3A DSP 3400A HW Co-Sim Configuration Files
System Generator comes with HW Co-Sim configuration files that first need to be loaded
into the Spartan-3A DSP 3400A CompactFlash card with a CompactFlash Reader.
1.
Optionally Backup the Spartan-3A DSP 3400A Demo Files
The Spartan-3A DSP 3400A CompactFlash card comes with a series of demo files that you
might want to re-load and exercise later.
a.
Connect the CompactFlash Reader to the PC. This is usually done through a USB
port.
b.
Insert the CompactFlash card into a CompactFlash Reader.
c.
Click on the MyComputer icon, then select the Removable Disk drive that
represents the CompactFlash Reader..
d. Create or open a backup folder on the PC and copy the content of the
CompactFlash card to that folder for later use.
Note: For the following steps, 'e:' is assumed to be the drive name associated with the
CompactFlash reader.
2.
Re-Format the CompactFlash Card
The card needs to be re-formatted to a FAT16 file system before the System Generator files
can be transferred. You use the mkdosfs utility to format the card.
a.
Download the mkdosfs program from the Xilinx URL address:
http://www.xilinx.com/products/boards/ml310/current/utilities/mkdosfs.zip.
b.
Extract to folder C:/mkdosfs
c.
Open a Windows shell by selecting Start > Run..., then type cmd in the Run dialog
box and click OK.
d. In the shell, move to the mkdosfs folder:
cd C:\mkdosfs
Caution! In the following step, make sure the drive name (e.g., 'e:' in this case) is specified
correctly for the Compact Flash Removable Disk. Otherwise, the information on the mistakenly
targeted drive will be erased and the drive will be re-formatted.
e.
Type the following mkdosfs command after the Windows command prompt:
mkdosfs -v -F 16 e:
The content of the Compact Flash card should be wiped clean and re-formatted.
3.
Copy the Sysgen configuration files to the Compact Flash card
Note: For reference, the Sysgen files to be copied are located at the following pathname:
...<sysgen_tree>\plugins\bin\S3ADSP_DB_sysace_cf.zip
Invoke MATLAB on the PC, then enter the following command on the MATLAB
Command Line:
unzip(fullfile(xlFindSysgenRoot,'plugins/bin/S3ADSP_DB_sysace_cf.zip'),'e
:/')
Optional Step to set the Ethernet MAC Address and the IPv4 Address
Note: The following step may be necessary if the default MAC and IP addresses conflict with your
default network settings, or if you wish to co-simulate two or more ML506 boards concurrently. If not,
proceed to the next topic.
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Release 10.1.1 April, 2008
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After writing the data to the card, you will find two files, mac.dat and ip.dat, in the
card root directory. The mac.dat and ip.dat files specify the Ethernet MAC address
and IPv4 address associated with the board, respectively. These addresses are used to
uniquely identify a target board during Ethernet hardware co-simulation.
a.
Open mac.dat in a text editor and change the Ethernet MAC address. The MAC
address must be specified as a six pair of two-digit hexadecimal separated by
colons (e.g. 00:0a:35:11:22:33). All-zeros, broadcast, or multicast MAC
addresses are not supported.
a.
Open ip.dat in a text editor and change the IP address. The IP address must be
specified in IPv4 dotted decimal notation (e.g. 192.168.8.1). All-zeros,
broadcast, multicast, or loop-back IP address are not supported. After changing
the IP address for the ML506 board, update the IP address for the network
connection on the PC accordingly as mentioned in the topic Setup the Local Area
Network on the PC. For direct connection, the ML506 and the PC must be on the
same subnet. Otherwise, the ML506 IP address should be reachable from the PC
and vice versa.
Setup the Spartan-3A 3400A Development Board
The figure below illustrates the Spartan-3A 3400A Board (Rev C) components of interest in
this setup procedure:
Power Switch
+12V Power Connector
Ethernet Mode Select
jumper (JP2)
LYR178-101C (Rev C)
Ethernet Port
Configuration
Address
DIP Switches (S2)
System ACE
Reset Button
Compact Flash Card
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LCD
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Installing Your Hardware Co-Simulation Board
The figure below illustrates the Spartan-3A 3400A Board (Rev D) components of interest in
this setup procedure:
Ethernet Mode Select
Ethernet Port
LYR178-101D (Rev D)
Configuration
Address
DIP Switches (S2)
System ACE
Reset Button
LCD
Compact Flash Card
Power Switch
+5V Power Connector
1.
Position the Spartan-3A 3400A Development Board as shown above with the LCD
display at the bottom.
2.
Make sure the power switch is in the OFF position.
3.
As shown below, Eject the CompactFlash card from the CompactFlash Reader.
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4.
Remove the CompactFlash card from the CompactFlash Reader.
5.
Locate the CompactFlash card slot (on the back side of the Spartan-3A 3400A board)
and carefully insert the CompactFlash card with its front label facing away from the
board. The figure below shows the back side of a board with the ConpactFlash card
properly inserted.
Note: The CompactFlash card provided with your board might differ.
Caution! Be careful when inserting or removing the CompactFlash card from the slot. Do not
force it.
6.
If you are using a “Rev C” 3400A Development Platform, plug the +12V power supply
adapter cable into the power connector. Plug in the power supply into AC power.
If you are using a “Rev D” 3400A Development Platform, plug the +5V power supply
adapter cable into the power connector. Plug in the power supply into AC power.
Caution! Make sure you use an appropriate power supply with the correct voltage
and power ratings.
7.
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Using the RJ45 Male/Male Ethernet Cable, connect the Ethernet connector on the
Spartan-3A 3400A board directly to the Ethernet connector on the host PC.
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Installing Your Hardware Co-Simulation Board
8.
Set the S2 Configuration Address DIP Switches as follows:
1:off, 2:on, 3:off, 4:on, 5:off, 6:on, 7:on, 8:off
9.
Set the Ethernet Mode Select jumper JP2 to pin 1 and pin 2 (the default GMII).
10. Verify the Configuration Settings
a.
Turn the target board Power switch ON.
b. As shown below, check the information displayed on the 16-character 2-line LCD
screen of the board. If no error occurred, the Ethernet MAC address (without
colons) should appear on the first line of the display and the IPv4 address should
appear on the second line.
c.
If the LCD display does not show the information correctly, press the System ACE
Reset button to reconfigure the FPGA.
11. Verify the Ethernet Interface and Connection Status
a.
To ensure the board is reachable by the host, issue ICMP ping from the host to
check the connectivity. For example, type "ping 192.168.8.1" on a console to test the
connectivity to a board with IP address 192.168.8.1.
b. The target FPGA listens on the UDP port 9999. Please ensure the underlying
network does not block the associated traffic when network-based Ethernet
configuration is used. This does not affect point-to-point Ethernet configuration.
For indepth reference information on the Spartan-3A 3400A Development Platform, plese
refer to the following online manual:
http://www.xilinx.com/bvdocs/ipcenter/user_guide_user_manual/s3a-dsp-3400auserguide.pdf
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Installing an ML402 Board for JTAG Hardware Co-Simulation
The following procedure describes how to install and setup the hardware and software
required to run JTAG Hardware Co-Simulation on an ML402 board.
Assemble the Required Hardware
1.
2.
Xilinx Virtex-4 SX ML402 Platform which includes the following:
a.
Virtex-4 ML402 board
b.
5V Power Supply bundled with the ML402 kit
c.
CompactFlash Card
You also need the following items on hand:
a.
Xilinx Parallel Cable IV with associated Power Jack splitter cable or Xilinx
Platform USB Cable and a 14-pin ribbon cable.
b.
CompactFlash Reader for the PC.
Install the Software on the Host PC
•
System Generator version as specified in the current System Generator Release Notes.
•
Xilinx ISE Software version as specified in the current System Generator Release
Notes.
Setup the ML402 Board
The figure below illustrates the ML402 components of interest in this JTAG setup
procedure:
FPGA & CPU
Debug Port
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1.
Position the ML402 board so the Virtex™-4 and Xilinx logos are oriented near the top
edge of the board.
2.
Make sure the power switch, located in the upper-right corner of the board, is in the
OFF position.
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3.
If you are using a Xilinx Parallel Cable IV, follow steps 3a through 3d.
a.
Connect the DB25 Plug Connector on the Xilinx Parallel Cable IV to the IEEE-1284
compliant PC Parallel (Printer) Port Connector .
b. Using the narrow (14 pin) 6” High Performance Ribbon cable, connect the pod end
of the Xilinx Parallel Cable IV to the FPGA & CPU Debug Port (shown above) on
the ML402 Board.
c.
Connect the attached Power Jack cable to the Keyboard/Mouse connector on the
PC.
d. If necessary, connect the male end of the Keyboard/Mouse cable to the associated
female connector on the Xilinx Power Jack cable (splitter cable) .
4.
If you are using a Xilinx Platform Cable USB, follow step 4a and 4b..
a.
Connect the Xilinx Platform Cable USB to a USB port on the PC.
b. Using the narrow (14 pin) 6” High Performance Ribbon cable, connect the pod end
of the Xilinx Platform Cable USB to the FPGA & CPU Debug Port (shown above)
on the ML402 Board.
5.
Connect the AC power cord to the power supply brick. Plug the power supply adapter
cable into the ML402 board. Plug in the power supply to AC power.
Caution! Make sure you use an appropriate power supply with correct voltage and power
ratings.
6.
Turn the ML402 Board Power switch ON.
Supporting New Platforms through JTAG Hardware Co-Simulation
System Generator provides a generic interface that uses JTAG and a Xilinx programming
cable (e.g., Parallel Cable IV or Platform Cable USB) to communicate with FPGA
hardware. This takes advantage of the ability of JTAG to extend System Generator's
hardware in the simulation loop capability to numerous other FPGA platforms.
Hardware Requirements
An FPGA platform can support the JTAG hardware co-simulation interface, provided it
includes the following hardware components:
•
A Xilinx FPGA part that is available in System Generator as a supported device (i.e., a
device that can be chosen in the Part field of the System Generator block dialog box);
•
An on-board oscillator that supplies the FPGA with a free-running clock source;
•
A JTAG header that provides access to the FPGA.
Supporting New Platforms
Although the JTAG hardware co-simulation interface is generic, an FPGA platform must
provide its own board support package before it can be supported in System Generator. A
board support package is comprised of four files that provide information about the board,
or platform. A number of FPGA platforms already have board support packages available.
See Hardware Co-Simulation Installation for more information on how to download these
files.
You may have an FPGA platform that does not have a hardware co-simulation board
support package. In this case, you can create your own, assuming your platform meets the
specified Hardware Requirements. Creating a new board support package for a platform is
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a straightforward process. System Generator provides a utility, called the System
Generator Board Description Builder (SBDBuilder), that allows you to create new board
support packages in a graphical environment. It is also possible to define board support
packages manually by editing a series of template files that are included in the System
Generator software tree.
SBDBuilder Dialog Box
After invoking SBDBuilder, the main dialog box will appear as shown below:
Once the main dialog box is open, you may create a board support package by filling in the
required fields described below:
Board Name: Tells a descriptive name of the board. This is the name that will be listed in
System Generator when selecting your JTAG hardware co-simulation platform for
compilation.
System Clock: JTAG hardware co-simulation requires an on-board clock to drive the
System Generator design. The fields described below specify information about the
board's system clock:
•
Frequency (MHz): Specifies the frequency of the on-board system clock in MHz.
•
Pin Location: Specifies the FPGA input pin to which the system clock is connected.
JTAG Options: System Generator needs to know several things about the FPGA board's
JTAG chain to be able to program the FPGA for hardware co-simulation. The topic
Obtaining Platform Information describes how and where to find the information required
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for these fields. If you are unsure of the specifications of your board, please refer to the
manufacturer's documentation. The fields specific to JTAG Options are described below:
•
Boundary Scan Position: Specifies the position of the target FPGA on the JTAG chain.
This value should be indexed from 1. (e.g. the first device in the chain has an index of
1, the second device has an index of 2, etc.)
•
IR Lengths: Specifies the lengths of the instruction registers for all of the devices on
the JTAG chain. This list may be delimited by spaces, commas, or semicolons.
•
Detect: This action attempts to identify the IR Lengths automatically by querying the
FPGA board. The board must be powered and connected to a Parallel Cable IV for this
to function properly. Any unknown devices on the JTAG chain will be represented
with a "?" in the list, and must be specified manually.
Targetable Devices: This table displays a list of available FPGAs on the board for
programming. This is not a description of all of the devices on the JTAG chain, but rather a
description of the possible devices that may exist at the aforementioned boundary scan
position. For most boards, only one device needs to be specified, but some boards may
have alternate, e.g., a choice between an xcv1000 or an xcv2000 in the same socket. Use the
Add and Delete buttons described below to build the device list:
•
Add: Brings up a menu to select a new device for the board. As shown in the figure
below, devices are organized by family, then part name, then speed, and finally the
package type.
•
Delete: Remove the selected device from the list.
Non-Memory-Mapped Ports: You can add support for your own board-specific ports
when creating a board support package. Board-specific ports are useful when you have onboard components (e.g., external memories, DACs, or ADCs) that you would like the
FPGA to interface to during hardware co-simulation. Board specific ports are also referred
to as non-memory-mapped because when the design is compiled for hardware cosimulation, these ports will be mapped to their physical locations, rather than creating
Simulink ports. See Specifying Non-Memory Mapped Ports for more information. The
Add, Edit, and Delete buttons provide the controls needed for configuring non-memory
mapped ports.
•
Add: Brings up the dialog to enter information about the new port.
•
Edit: Make changes to the selected port.
•
Delete: Remove the selected port from the list.
Help: Displays this documentation.
Load: Fill in the form with values stored in an SBDBuilder Saved Description XML file.
This file is automatically saved with every plugin that you create, so it is useful for
reloading old plugin files for easy modification.
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Save Zip: Prompts you for a filename and a target pathname. This will create a zip file with
all of the plugin files for System Generator. The zip will be in a suitable format for passing
to the System Generator xlInstallPlugin function.
Exit: Quit the application.
Specifying Non-Memory Mapped Ports
You may use SBDBuilder to specify the non-memory mapped ports for your FPGA
platform. When you choose to Add or Edit a non-memory mapped port from the main
dialog, the port editor dialog will come up as shown below.
The port editor dialog presents the following controls for port configuration:
Port Options: Specifies the options that will affect the entire port.
•
Port Name: This is the name that will describe the port in System Generator. It should
be a MATLAB-compatible name (begins with a letter, followed by only letters,
numbers, and underscores).
•
Input/Output: Specifies the direction of the port.
New Pin: This is the entry point to add pins to a port. Ports may consist of a single pin for
a Boolean value, or multiple pins for a vector or bus.
•
Pin LOC: Defines the absolute placement of the pin within the FPGA by specifying a
location constraint. It is necessary to define this for every pin to make sure that the
FPGA programming corresponds to the actual hardware connections.
•
PULLUP: A constraint that can be applied to each pin. It guarantees a logic High level
to allow 3-stated nets to avoid floating when not being driven.
•
FAST: A constraint that can be applied to each pin. It increases the speed of an IOB
output. FAST produces a faster output but may increase noise and power
consumption.
•
Add Pin: Add a pin to the port. Note that the pin is not part of the port until this
button is selected.
Note: Pressing 'enter' while the cursor is in the Pin LOC field is equivalent to pressing this
button.
Pin List:
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•
Index: (Cannot edit directly) Since a port can be more than one bit, it is represented as
a vector of pins. The index indicates which bit position a particular pin represents in
the port. Zero is the least-significant bit.
•
Move Up/Down: Move the selected pin up or down in the pin list. This is useful to
correct the vector bit-ordering of the port.
•
Delete Pin: Removes the selected pin from the list.
Save and Start New: Save the port to the board support package. The form will then be
cleared so that you may enter a new port.
Save and Close: Save the port to the board support package and return to the main screen.
Cancel: Discard changes to the current port and return to the main screen.
When you are finished entering a port, it will look similar to the dialog box shown below:
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Saving Plugin Files
Once you have filled out the dialog box with information about your platform, it should
resemble the dialog box shown below:
At this point, you can save the board support package into a System Generator plugin zip
file or as the raw board support package files described in the topic Board Support Package
Files, plus the additional SBDBuilder files described below:
260
•
yourboard.xml: This is the SBDBuilder Saved Description, which allows SBDBuilder
to reload plugins you have previously created. The name you select for this file
('yourboard') will propagate into the names of the other files as well.
•
yourboard_libgen.m: Automates the process of creating the gateways for the nonmemory-mapped ports on this device. Running this script results in the creation a
library like that shown below:
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Board Support Package Files
An FPGA platform that supports JTAG hardware co-simulation is defined in System
Generator by its board support package. This package tells System Generator useful
information about the platform, such as the appropriate part settings and additional
information related to the JTAG and Boundary Scan interface provided by the platform. A
board support package is comprised of the files listed below:
Note: In this document, three of the filenames are prefixed by the name 'yourboard'. This prefix
should be replaced with a moniker suitable for 'your board' (e.g., xtremedspkit, mblazedemo).
1.
xltarget.m – Tells System Generator that your FPGA platform is a compilation target.
There is a unique xltarget.m file for each compilation target. This function tells the tool
the name of the compilation target (this name is shown in the compilation target field
of the System Generator block dialog box) and also the name of the function where it
can look for information about the particular board.
2.
yourboard_target.m – Configures the System Generator block dialog box with
information about the FPGA platform, including device and part information, clock
frequency, and the location of the clock pin.
3.
yourboard_postgeneration.m – Tells System Generator the scripts to run after HDL
netlist generation in order to produce an FPGA configuration file that is suitable for
your platform. It also specifies non-System Generator block dialog box related
information, including the position of the device in the platform's Boundary Scan
chain and the instruction register lengths of each device. This function is referred to as
a post-generation function.
4.
yourboard.ucf – User Constraints File (UCF) for the FPGA platform. Specifies clock
pin location and frequency, and optionally constrains any board-specific ports.
Included in the System Generator software tree are templates for the files listed above. If
you would like to manually support a new board, you may customize each of the four
template files with information that is specific to your platform. You must also rename the
files by substituting a suitable name in place of the 'yourboard' prefix.
Each template is fully annotated with step-by-step instructions that indicate which fields
should be modified, and the types of values that should be given to these fields. The fields
that must be modified are underlined using "~~~" notation. The template files can be
found in the sysgen/hwcosim/jtag/templates directory of your System Generator
install tree.
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Obtaining Platform Information
SBDBuilder (or alternatively, the board support package template files) require certain
information about your FPGA platform. The table below lists the information you need.
Information
Description
Clock pin location
Pin location constraint for the FPGA system clock source.
Clock period
Period constraint for the FPGA system clock source.
Device position in
the Boundary Scan
Chain
Tells the position of the target FPGA in the platform's Boundary
Scan Chain. Indexing begins at 1, with device 1 being the first
device in the chain.
Instruction register
lengths
Instruction register length of every device in the Boundary Scan
Chain.
You may obtain the clock pin location and period from any number of possible sources,
including the vendor documentation, existing constraints files, or vendor online
documentation/support.
If you do not know which devices are in your platform's boundary scan chain, you may
use iMPACT to assist you in finding this information. iMPACT is a tool that is included
with the Xilinx ISE software that allows you to perform device configuration and file
generation functions. When the tool is invoked, it automatically detects the contents of
your platform's boundary scan chain, and displays these contents graphically, as shown
below.
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Once you have determined which devices are in the Boundary Scan Chain, you must
determine the instruction register lengths for each device. The table below specifies the
instruction register lengths for various Xilinx families. You may use the auto detection
capability of SBDBuilder to determine the instruction register lengths. If this utility does
not work, you may use the following table to find the instruction register lengths for a
particular part family.
Family
IR Length
XC9500 / XC9500XL / XC9500XV
8
XC1800 / XC18V00
8
XC4000XL/XLA
3
Spartan-XL
3
System_ACE-CF
8
Virtex / Virtex-E(EM)
5
Spartan-II / Spartan-IIE
5
Virtex-II
6
Spartan-3
6
Spartan-3E
6
Spartan-3A/Spartan-3AN
6
Spartan-3A DSP
6
Virtex-II Pro 2, 4, 7
10
Virtex-II Pro 20, 30, 40, 50, 70, 100
14
Virtex-II Pro 125
16
Virtex-4 LX
10
Virtex-4 SX
10
Virtex-4 FX 12, 20
10
Virtex-4 FX 40, 60, 100, 140
14
Virtex-5 LX
10
XCR3000XL
5
XCR3000A / XCR3128
4
XCR3320 / XCR3960
5
XCR5128 / XCR5032C / XCR5064C / XCR5128C
4
CoolRunner-II
8
Platform Flash XCFxxS
8
Platform Flash XCFxxP
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Manual Specification of Board-Specific Ports
You can manually specify your own board-specific ports when creating a board support
package. To define board-specific ports for your FPGA platform, you must do the
following:
•
Add all board-specific ports to the yourboard.ucf template file. Each constraint
should be accompanied by a special comment, <port> contingent, where <port>
is the name of the board specific port. When System Generator compiles a model for
hardware, it creates a custom UCF file. Constraints associated with signals that aren't
used in the model are removed from the custom UCF file.
Example constraints for ports adc1_d(0) and adc1_d(1):
net adc1_d(0) loc = af20; # adc1_d contingent
net adc1_d(1) loc = ad18; # adc1_d contingent
•
Declare all board-specific ports in the yourboard_postgeneration.m function.
Port Name
(Must match UCF)
Width
non_mm_ports.('adc1_d') = ('in',14);
Direction
Note: Bi-directional ports are currently not supported.
Include this line in yourboard_postgeneration.m function:
params.('non_memory_mapped_ports') = non_mm_ports;
•
Customize a gateway with the board-specific port information:
♦
Create a library and add a gateway
♦
Name the Gateway with the name of your board specific port (this name must
match the port name used in the post-generation function and UCF file)
♦
Select the Gateway by clicking on it
♦
In the MATLAB command window, type the following
> xlSetNonMemMap(gcb, 'Xilinx', 'jtaghwcosim')
♦
Save the library
You are now ready to use your board-specific gateway in System Generator. When you
include the gateway in your model, you must make sure the signals that drive (or are
driven by) the gateway have widths that match the widths of the ports in hardware. You
can force the width of a signal driving a gateway out by preceding it with a convert block.
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Note: A subsystem (as shown below) is a convenient place to store the gateway out and convert
block pairs.
Providing Your Own Top Level
When a model is compiled for JTAG hardware co-simulation, System Generator produces
a generic top-level HDL entity for the design. This entity instantiates the logic required by
the model and the interfacing logic required for JTAG hardware co-simulation.
Sometimes your platform may have a special requirement that precludes you from using
this generic top level. For example, your platform may have components that rely on
clocks that are generated by a DCM that resides in the platform's FPGA. In these situations,
System Generator allows you to use your own top-level netlist when it compiles the model
into hardware.
Note: If you choose to use your own top-level component, you must provide a previously
synthesized version (.ngc, .edf, .edn) to System Generator.
Note: Your top-level component must instantiate the generic JTAG hardware co-simulation top-level
component. The component instantiation must include the required clocking signals, plus any boardspecific I/O ports your board may support. An example component instantiation is provided below:
component jtagcosim_top port (
-- required clocking ports
sys_clk : in std_logic;
cosim_clk : out std_logic;
sys_clk_buf : out std_logic;
-- board specific ports
adc1_d : in std_logic_vector(13 downto 0);
dac1_d : out std_logic_vector(13 downto 0);
dac1_div0 : out std_logic;
dac1_div1 : out std_logic;
dac1_mod0 : out std_logic;
dac1_mod1 : out std_logic;
dac1_reset : out std_logic
);
end component;
You may specify your own top-level netlist in yourboard_postgeneration.m as
follows:
params.vendor_toplevel = 'yourboard_toplevel';
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Here yourboard_toplevel is the name of the pre-compiled, top-level netlist component
you would like System Generator to use for the top level. You must also tell System
Generator the netlist file names that are associated with the top-level component. These
files are specified as shown below in yourboard_postgeneration.m.
params.vendor_netlists = {'yourboard_toplevel.ngc','foo.edf'};
Installing Board-Support Packages
SBDBuilder can generate a plugin zip file for your board support package that may be
installed automatically using the xlInstallPlugin utility provided with System Generator.
You may manually install the board support package files if an appropriate plugin zip file
is not provided. This topic describes how to install the files manually in your System
Generator software tree.
Plugins Directory
The System Generator software provides a special directory in which the board support
package files for new compilation targets can be added. This directory,
plugins/compilation, provides a repository for System Generator compilation target
plugins, and has unique properties that are discussed later in this topic. Your System
Generator software tree should resemble the tree hierarchy shown below.
The board support package files for you platform should be saved in a subdirectory, or
series of subdirectories, under the plugins/compilation directory.
Note: All configuration files associated with a board support package must be saved in the same
directory.
System Generator searches this directory (and subdirectories) for compilation targets.
Recall that the xltarget.m file tells System Generator the platform should be used as a
compilation target. When the tool searches the plugins/compilation directory, it adds
a compilation target to the System Generator block dialog box for every xltarget.m file
that it encounters.
The System Generator block dialog box Compilation submenus mirror the directory
structure under the plugins/compilation directory. When you create a new directory,
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or directory hierarchy, for a board support package, the names of the directories define the
taxonomy of the compilation target submenus.
Detecting New Packages
In order for System Generator to recognize the new target, you must tell it to search for
new compilation targets by entering the following command in the MATLAB command
window:
xlrehash_xltarget_cache
You can now select the FPGA platform from the list of compilation targets in the System
Generator block dialog box.
Note: If you have a System Generator block dialog box open when you enter this command, it will
not show up until you close and re-open the dialog box.
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Importing HDL Modules
Sometimes it is important to add one or more existing HDL modules to a System Generator
design. The System Generator Black Box block allows VHDL, Verilog, and EDIF to be
brought into a design. The Black Box block behaves like other System Generator blocks - it
is wired into the design, participates in simulations, and is compiled into hardware. When
System Generator compiles a Black Box block, it automatically wires the imported module
and associated files into the surrounding netlist.
The Black Box Interface
Black Box HDL Requirements
and Restrictions
Details the requirements and restrictions for VHDL,
Verilog, and EDIF associated with black boxes.
Black Box Configuration Wizard
Describes how to use the Black Box Configuration
Wizard.
Black Box Configuration MFunction
Describes how to create a black box configuration Mfunction.
HDL Co-Simulation
Configuring the HDL Simulator
Explains how to configure ISE or ModelSim to cosimulate the HDL in the Black Box block.
Co-Simulating Multiple Black
Boxes
Describes how to co-simulate several Black Box blocks
in a single HDL simulator session.
Black Box Tutorial Example 1:
Importing a Core Generator
Module that Satisfies Black Box
HDL Requirements
Describes an approach that uses the System Generator
Black Box Configuration Wizard.
Black Box Tutorial Example 2:
Importing a Core Generator
Module that Needs a VHDL
Wrapper to Satisfy Black Box
HDL Requirements
Describes an approach that requires that you to
provide a VHDL core wrapper. Simulation issues are
also addressed.
Black Box Tutorial Example 3:
Importing a VHDL Module
Describes how to use the Black Box block to import
VHDL into a System Generator design and how to use
ModelSim to co-simulate.
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Black Box Tutorial Example 4:
Importing a Verilog Module
Demonstrates how Verilog black boxes can be used in
System Generator and co-simulated using ModelSim.
Black Box Tutorial Example 5:
Dynamic Black Boxes
Demonstrates dynamic black boxes using a transpose
FIR filter black box that dynamically adjusts to
changes in the widths of its inputs.
Black Box Tutorial Example 6:
Simulating Several Black Boxes
Simultaneously
Demonstrates how several System Generator Black
Box Blocks can be co-simulated simultaneously, using
only one ModelSim license while doing so.
Black Box Tutorial Exercise 7:
Advanced Black Box Example
Using ModelSim
Describes how to design a Black Box block with a
dynamic port interface and how to configure a black
box using mask parameters. Also, describes how to
assign generic values based on input port data types
and how to save black box blocks in Simulink libraries
for later reuse. How to specify custom scripts for
ModelSim HDL co-simulation is also covered.
Black Box HDL Requirements and Restrictions
An HDL component associated with a black box must adhere to the following System
Generator requirements and restrictions:
•
The entity name must not collide with any other entity name in the design.
•
Bi-directional ports are supported in HDL black boxes, however they will not be
displayed in the System Generator as ports; they only appear in the generated HDL
after netlisting.
•
For Verilog black boxes, the module and port names must be lower case and must
follow standard VHDL naming conventions.
•
Any port that is a clock or clock enable must be of type std_logic. (For Verilog black
boxes, ports must be of non-vector inputs, e.g., input clk.)
•
Clock and clock enable ports in black box HDL should be expressed as follows: Clock
and clock enables must appear as pairs (i.e., for every clock, there is a corresponding
clock enable, and vice-versa). Although a black box may have more than one clock
port, a single clock source is used to drive each clock port. Only the clock enable rates
differ.
•
Each clock name (respectively, clock enable name) must contain the substring clk, for
example my_clk_1 and my_ce_1.
•
The name of a clock enable must be the same as that for the corresponding clock, but
with ce substituted for clk. For example, if the clock is named src_clk_1, then the
clock enable must be named src_ce_1.
•
Falling-edge triggered output data cannot be used.
Black Box Configuration Wizard
System Generator provides a configuration wizard that makes it easy to associate a VHDL
or Verilog module to a Black Box block. The Configuration Wizard parses the VHDL or
Verilog module that you are trying to import, and automatically constructs a configuration
M-function based on its findings. It then associates the configuration M-function it
produces to the Black Box block in your model. Whether or not you can use the
configuration M-function as is depends on the complexity of the HDL you are importing.
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Sometimes the configuration M-function must be customized by hand to specify details
the configuration wizard misses. Details on the construction of the configuration Mfunction can be found in the topic Black Box Configuration M-Function.
Using the Configuration Wizard
The Black Box Configuration Wizard opens automatically when a new black box block is
added to a model.
Note: Before running the Configuration Wizard, ensure the VHDL or Verilog you are importing
meets the specified Black Box HDL Requirements and Restrictions.
For the Configuration Wizard to find your module, the model must be saved in the same
directory as the module you are trying to import. This means, in particular, that the model
must be saved to same directory.
Note: The wizard only searches for .vhd and .v files in the same directory as the .mdl file. If the
wizard does not find any files it issues a warning and the black box is not automatically configured.
The warning looks like the following:
After searching the model's directory for .vhd and .v files, the Configuration Wizard
opens a new window that lists the possible files that can be imported. An example
screenshot is shown below:
You can select the file you would like to import by selecting the file, and then pressing the
Open button. At this point, the configuration wizard generates a configuration M-function
and associates it with the black box block.
Note: The configuration M-function is saved in the model's directory as <module>_config.m,
where <module> is the name of the module that you are importing.
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Configuration Wizard Fine Points
The configuration wizard automatically extracts certain information from the imported
module when it is run, but some things must be specified by hand. These things are
described below:
Note: The configuration function is annotated with comments that instruct you where to make these
changes.
•
If your model has a combinational path, you must call the tagAsCombinational
method of the block's SysgenBlockDescriptor object.
•
The Configuration Wizard only knows about the top-level entity that is being
imported. There are typically other files that go along with this entity. These files must
be added manually in the configuration M-function by invoking the addFile method
for each additional file.
•
The Configuration Wizard creates a single-rate black box. This means that every port
on the black box runs at the same rate. In most cases, this is acceptable. You may want
to explicitly set port rates, which can result in a faster simulation time.
Black Box Configuration M-Function
An imported module is represented in System Generator by a Black Box block. Information
about the imported module is conveyed to the black box by a configuration M-function.
This function defines the interface, implementation, and the simulation behavior of the
black box block it is associated with. More specifically, the information a configuration Mfunction defines includes the following:
•
Name of the top-level entity for the module;
•
VHDL or Verilog language selection;
•
Port descriptions;
•
Generics required by the module;
•
Clocking and sample rates;
•
Files associated with the module;
•
Whether the module has any combinational paths.
The name of the configuration M-function associated with a black box is specified as a
parameter in the black box parameters dialog box (parity_block_config.m in the
example shown below).
Configuration M-functions use an object-based interface to specify black box information.
This interface defines two objects, SysgenBlockDescriptor and SysgenPortDescriptor.
When System Generator invokes a configuration M-function, it passes the function a block
descriptor:
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function sample_block_config(this_block)
A SysgenBlockDescriptor object provides methods for specifying information about the
black box. Ports on a block descriptor are defined separately using port descriptors.
Language Selection
The black box can import VHDL and Verilog modules. SysgenBlockDescriptor provides a
method, setTopLevelLanguage, that tells the black box what type of module you are
importing. This method should be invoked once in the configuration M-function. The
following code shows how to select between the VHDL and Verilog languages.
VHDL Module:
this_block.setTopLevelLanguage('VHDL');
Verilog Module:
this_block.setTopLevelLanguage('Verilog');
Note: The Configuration Wizard automatically selects the appropriate language when it generates
a configuration M-function.
Specifying the Top-Level Entity
You must tell the black box the name of the top-level entity that is associated with it.
SysgenBlockDescriptor provides a method, setEntityName, which allows you to specify
the name of the top-level entity.
Note: Use lower case text to specify the entity name.
For example, the following code specifies a top-level entity named foo.
this_block.setEntityName('foo');
Note: The Configuration Wizard automatically sets the name of the top-level entity when it
generates a configuration M-function.
Defining Block Ports
The port interface of a black box is defined by the block's configuration M-function. Recall
that black box ports are defined using port descriptors. A port descriptor provides
methods for configuring various port attributes, including port width, data type, binary
point, and sample rate.
Adding New Ports
When defining a black box port interface, it is necessary to add input and output ports to
the block descriptor. These ports correspond to the ports on the module you are importing.
In your model, the black box block port interface is determined by the port names that are
declared on the block descriptor object. SysgenBlockDescriptor provides methods for
adding input and output ports:
Adding an input port:
this_block.addSimulinkInport('din');
Adding an output port:
this_block.addSimulinkOutport('dout');
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The string parameter passed to methods addSimulinkInport and addSimulinkOutport
specifies the port name. These names should match the corresponding port names in
the imported module.
Note: Use lower case text to specify port names.
Adding a bidirectional port:
config_phase = this_block.getConfigPhaseString;
if (strcmpi(config_phase,'config_netlist_interface'))
this_block.addInoutport('bidi');
% Rate and type info should be added here as well
end
Bi-directional ports are supported only during the netlisting of a design and will not
appear on the System Generator diagram; they only appear in the generated HDL. As
such, it is important to only add the bi-drirectional ports when System Generator is
generating the HDL. The if-end conditional statement is guarding the execution of the
code to add-in the bi-directional port.
It is also possible to define both the input and output ports using a single method call. The
setSimulinkPorts method accepts two parameters. The first parameter is a cell array of
strings that define the input port names for the block. The second parameter is a cell array
of strings that define the output port names for the block.
Note: The Configuration Wizard automatically sets the port names when it generates a
configuration M-function
Obtaining a Port Object
Once a port has been added to a block descriptor, it is often necessary to configure
individual attributes on the port. Before configuring the port, you must obtain a descriptor
for the port you would like to configure. SysgenBlockDescriptor provides methods for
accessing the port objects that are associated with it. For example, the following method
retrieves the port named din on the this_block descriptor:
Accessing a SysgenPortDescriptor object:
din = this_block.port('din');
In the above code, an object din is created and assigned to the descriptor returned by the
port function call.
SysgenBlockDescriptor also provides methods, inport and outport, that return a port
object given a port index. A port index is the index of the port (in the order shown on the
block interface) and is some value between 1 and the number of input/output ports on the
block. These methods are useful when you need to iterate through the block's ports (e.g.,
for error checking).
Configuring Port Types
SysgenPortDescriptor provides methods for configuring individual ports. For example,
assume port dout is unsigned, 12 bits, with binary point at position 8. The code below
shows one way in which this type can be defined.
dout = this_block.port('dout');
dout.setWidth(12);
dout.setBinPt(8);
dout.makeUnsigned();
The following also works:
dout = this_block.port('dout');
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dout.setType('Ufix_12_8');
The first code segment sets the port attributes using individual method calls. The second
code segment defines the signal type by specifying the signal type as a string. Both code
segments are functionally equivalent.
The black box supports HDL modules with 1-bit ports that are declared using either single
bit port (e.g., std_logic) or vectors (e.g., std_logic_vector(0 downto 0)) notation. By default,
System Generator assumes ports to be declared as vectors. You may change the default
behavior using the useHDLVector method of the descriptor. Setting this method to true
tells System Generator to interpret the port as a vector. A false value tells System
Generator to interpret the port as single bit.
dout.useHDLVector(true); % std_logic_vector
dout.useHDLVector(false); % std_logic
Note: The Configuration Wizard automatically sets the port types when it generates a configuration
M-function.
Configuring Bi-Directional Ports for Simulation
Bi-directional ports (or inout ports) are supported only during the generation of the HDL
netlist, that is, bi-directional ports will not show up in the System Generator diagram. By
default, bi-directional ports will be driven with 'X' during simulation. It is possible to
overwrite this behavior by associating a data file to the port. Be sure to guard this code
since bi-directional ports can only be added to a block during the config_netlist_interface
phase.
if
(strcmpi(this_block.getConfigPhaseString,'config_netlist_interface'))
bidi_port = this_block.port('bidi');
bidi_port.setGatewayFileName('bidi.dat');
end
In the above example, a text file "bidi.dat" is used during simulation to provide stimulation
to the port. The data file should be a text file, where each line represents the signal driven
on the port at each simulation cycle. For example, a 3-bit bi-directional port that is
simulated for 4 cycles might have the following data file:
ZZZ
110
011
XXX
Simulation will return with an error if the specified data file cannot be found.
Configuring Port Sample Rates
The black box block supports ports that have different sample rates. By default, the sample
rate of an output port is the sample rate inherited from the input port (or ports, if the inputs
run at the same sample rate). Sometimes it is necessary to explicitly specify the sample rate
of a port (e.g., if the output port rate is different than the block's input sample rate).
Note: When the inputs to a black box have different sample rates, you must specify the sample rates
of every output port.
SysgenPortDescriptor provides a method, setRate, which allows you to explicitly set the
rate of a port.
Note: The rate parameter passed to the setRate method is not necessarily the Simulink sample rate
of that the port runs at. Instead, it is a positive Integer value that defines the ratio between the desired
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port sample period and the Simulink system clock period defined by the System Generator block
dialog box.
Assume you have a model in which the Simulink system period value for the model is
defined as 2 sec. Also assume, the example dout port is assigned a rate of 3 by invoking
the setRate method as follows:
dout.setRate(3);
A rate of 3 means that a new sample is generated on the dout port every 3 Simulink system
periods. Since the Simulink system period is 2 sec, this means the Simulink sample rate of
the port is 3 x 2 = 6 sec.
Note: If your port is a non-sampled constant, you may define it as so in the configuration M-function
using the setConstant method of SysgenPortDescriptor. You can also define a constant by passing
Inf to the setRate method.
Dynamic Output Ports
A useful feature of the black box is its ability to support dynamic output port types and
rates. For example, it is often necessary to set an output port width based on the width of
an input port. SysgenPortDescriptor provides member variables that allow you to
determine the configuration of a port. You can set the type or rate of an output port by
examining these member variables on the block's input ports.
For example, you can obtain the width and rate of a port (in this case din) as follows:
input_width = this_block.port('din').width;
input_rate = this_block.port('din').rate;
Note: A black box's configuration M-function is invoked at several different times when a model is
compiled. The configuration function may be invoked before the data types and rates have been
propagated to the black box.
The SysgenBlockDescriptor object provides Boolean member variables
inputTypesKnown and inputRatesKnown that tell whether the port types and rates
have been propagated to the block. If you are setting dynamic output port types or rates
based on input port configurations, the configuration calls should be nested inside
conditional statements that check that values of inputTypesKnown and
inputRatesKnown.
The following code shows how to set the width of a dynamic output port dout to have the
same width as input port din:
if (this_block.inputTypesKnown)
dout.setWidth(this_block.port('din').width);
end
Setting dynamic rates works in a similar manner. The code below sets the sample rate of
output port dout to be twice as slow as the sample rate of input port din:
if (this_block.inputRatesKnown)
dout.setRate(this_block.port('din').rate*2);
end
Black Box Clocking
In order to import a multirate module, you must tell System Generator information about
the module's clocking in the configuration M-function. System Generator treats clock and
clock enables differently than other types of ports. A clock port on an imported module
must always be accompanied by a clock enable port (and vice versa). In other words, clock
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and clock enables must be defined as a pair, and exist as a pair in the imported module.
This is true for both single rate and multirate designs.
Note: Although clock and clock enables must exist as pairs, System Generator drives all clock ports
on your imported module with the FPGA system clock. The clock enable ports are driven by clock
enable signals derived from the FPGA system clock.
SysgenBlockDescriptor provides a method, addClkCEPair, which allows you to define
clock and clock enable information for a black box. This method accepts three parameters.
The first parameter defines the name of the clock port (as it appears in the module). The
second parameter defines the name of the clock enable port (also as it appears in the
module).
The port names of a clock and clock enable pair must follow the naming conventions
provided below:
•
The clock port must contain the substring clk
•
The clock enable must contain the substring ce
•
The strings containing the substrings clk and ce must be the same (e.g., my_clk_1
and my_ce_1).
The third parameter defines the rate relationship between the clock and the clock enable
port. The rate parameter should not be thought of as a Simulink sample rate. Instead, this
parameter tells System Generator the relationship between the clock sample period, and
the desired clock enable sample period. The rate parameter is an integer value that defines
the ratio between the clock rate and the corresponding clock enable rate.
For example, assume you have a clock enable port named ce_3 that would like to have a
period three times larger than the system clock period. The following function call
establishes this clock enable port:
addClkCEPair('clk_3','ce_3',3);
When System Generator compiles a black box into hardware, it produces the appropriate
clock enable signals for your module, and automatically wires them up to the appropriate
clock enable ports.
Combinational Paths
If the module you are importing has at least one combinational path (i.e., a change on any
input can effect an output port without a clock event), you must indicate this in the
configuration M-function. SysgenBlockDescriptor object provides a
tagAsCombinational method that indicates your module has a combinational path. It
should be invoked as follows in the configuration M-function:
this_block.tagAsCombinational;
Specifying VHDL Generics and Verilog Parameters
You may specify a list of generics that get passed to the module when System Generator
compiles the model into HDL. Values assigned to these generics can be extracted from
mask parameters and from propagated port information (e.g., port width, type, and rate).
This flexible means of generic assignment allows you to support highly parametric
modules that are customized based on the Simulink environment surrounding the black
box.
The addGeneric method allows you to define the generics that should be passed to your
module when the design is compiled into hardware. The following code shows how to set
a VHDL Integer generic, dout_width, to a value of 12.
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addGeneric('dout_width','Integer','12');
It is also possible to set generic values based on port on propagated input port information
(e.g., a generic specifying the width of a dynamic output port).
Because a black box's configuration M-function is invoked at several different times when
a model is compiled, the configuration function may be invoked before the data types (or
rates) have been propagated to the black box. If you are setting generic values based on
input port types or rates, the addGeneric calls should be nested inside a conditional
statement that checks the value of the inputTypesKnown or inputRatesKnown
variables. For example, the width of the dout port can be set based on the value of din as
follows:
if (this_block.inputTypesKnown)
% set generics that depend on input port types
this_block.addGeneric('dout_width', ...
this_block.port('din').width);
end
Generic values can be configured based on mask parameters associated with a block box.
SysgenBlockDescriptor provides a member variable, blockName, which is a string
representation of the black box's name in Simulink. You may use this variable to gain
access the black box associated with the particular configuration M-function. For example,
assume a black box defines a parameter named init_value. A generic with name
init_value can be set as follows:
simulink_block = this_block.blockName;
init_value = get_param(simulink_block,'init_value');
this_block.addGeneric('init_value', 'String', init_value);
Note: You can add your own parameters (e.g., values that specify generic values) to the black box
by doing the following:
•
Copy a black box into a Simulink library or model;
•
Break the link on the black box;
•
Add the desired parameters to the black box dialog box.
Error Checking
It is often necessary to perform error checking on the port types, rates, and mask
parameters of a black box. SysgenBlockDescriptor provides a method, setError, which
allows you to specify an error message that is reported to the user. The string parameter
passed to setError is the error message that is seen by user.
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Black Box API
SysgenBlockDescriptor Member Variables
Type
Member
Description
String
entityName
Name of the entity or module.
String
blockName
Name of the black box block.
Integer
numSimulinkInports
Number of input ports on black box.
Integer
numSimulinkOutports
Number of output ports on the black
box.
Boolean
inputTypesKnown
true if all input types are defined, and
false otherwise.
Boolean
inputRatesKnown
true if all input rates are defined, and
false otherwise.
Array of
Doubles
inputRates
Array of sample periods for the input
ports (indexed as in inport(indx)).
Sample period values are expressed as
integer multiples of the Simulink
System Period value specified by the
master System Generator block
Boolean
error
true if an error has been detected, and
false otherwise.
Cell Array of
Strings
errorMessages
Array of all error messages for this
block.
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SysgenBlockDescriptor Methods
Method
280
Description
setTopLevelLanguage(language)
Declares language for the top-level entity (or
module) of the black box. language should be
'VHDL' or 'Verilog'.
setEntityName(name)
Sets name of the entity or module.
addSimulinkInport(pname)
Adds an input port to the black box. pname tells the
name the port should have.
addSimulinkOutport(pname)
Adds an output port to the black box. pname tells
the name the port should have.
setSimulinkPorts(in,out)
Adds input and output ports to the black box. in
(respectively, out) is a cell array whose element tell
the names to use for the input (resp., output) ports.
addInoutport(pname)
Adds a bi-directional port to the black box. pname
spcefies the name the port should have. Bidirectional ports can only be added during the
'config_netlist_interface' phase of configuration.
tagAsCombinational()
Indicate that the block has a combinational path (i.e.,
direct feedthrough) from an input port to an output
port.
addClkCEPair(clkPname, cePname,
rate)
Defines a clock/clock enable port pair for the block.
clkPname and cePname tell the names for the clock
and clock enable ports respectively. rate, a double,
tells the rate at which the port pair runs. The rate
must be a positive integer. Note the clock
(respectively, clock enable) name must contain the
substring clk (resp., ce). The names must be parallel
in the sense that the clock enable name is obtained
from the clock name by replacing clk with ce.
port(name)
Returns the SysgenPortDescriptor that describes a
given input port. indx tells the index of the port to
look for, and should be between 1 and
numInputPorts.
inport(indx)
Returns the SysgenPortDescriptor that describes a
given input port. indx tells the index of the port to
look for, and should be between 1 and
numInputPorts.
outport(indx)
Returns the SysgenPortDescriptor that describes a
given output port. indx tells the index of the port to
look for, and should be between 1 and
numOutputPorts.
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Method
Description
addGeneric(identifier, value)
Defines a generic (or parameter if using Verilog) for
the block. identifier is a string that tells the name of
the generic. value can be a double or a string. The
type of the generic is inferred from value's type. If
value is an integral double, e.g., 4.0, the type of the
generic is set to integer. For a non-integral double,
the type is set to real. When value is a string
containing only zeros and ones, e.g., `0101', the type
is set to bit_vector. For any other string value the
type is set to string.
addGeneric(identifier, type, value)
Explicitly specifies the name, type, and value for a
generic (or parameter if using Verilog) for the block.
All three arguments are strings. identifier tells the
name, type tells the type, and value tells the value.
addFile(fn)
Adds a file name to the list of files associated to this
black box. fn is the file name. Ordinarily, HDL files
are associated to black boxes, but any sorts of files
are acceptable. VHDL (respectively, Verilog) file
names should end in .vhd (resp., .v). The order in
which file names are added is preserved, and
becomes the order in which HDL files are compiled.
File names can be absolute or relative. Relative file
names are interpreted with respect to the location of
the .mdl or library .mdl for the design.
getDeviceFamilyName()
Gets the name of the FPGA device corresponding to
the Blackbox.
getConfigPhaseString
Returns the current configuration phase as a string.
A valid return string includes: config_interface,
config_rate_and_type, config_post_rate_and_type,
config_simulation, config_netlist_interface and
config_netlist.
setSimulatorCompilationScript
(script)
Overrides the default HDL co-simulation
compilation script that the black box generates.
script tells the name of the script to use. This method
can, for example, be used to short-circuit the
compilation phase for repeated simulations where
the HDL for the black box remains unchanged.
setError(message)
Indicates that an error has occurred, and records the
error message. message gives the error message.
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SysgenPortDescriptor Member Variables
Type
Member
Description
String
name
Tells the name of the port.
Integer
simulinkPortNumber
Tells the index of this port in Simulink.
Indexing starts with 1 (as in Simulink).
Boolean
typeKnown
True if this port's type is known, and
false otherwise.
String
type
Type of the port, e.g., UFix_<n>_<b>,
XFix_<n>_<b>, or Bool
Boolean
isBool
True if port type is Bool, and false
otherwise.
Boolean
isSigned
True if type is signed, and false
otherwise.
Boolean
isConstant
True if port is constant, and false
otherwise.
Integer
width
Tells the port width.
Integer
binpt
Tells the binary point position, which
must be an integer in the range
0..width.
Boolean
rateKnown
True if the rate is known, and false
otherwise.
Double
rate
Tells the port sample time. Rates are
positive integers expressed as MATLAB
doubles. A rate can also be infinity,
indicating that the port outputs a
constant.
SysgenPortDescriptor Methods
Method
282
Description
setName(name)
Sets the HDL name to be used for this port.
setSimulinkPortNumber(num)
Sets the index associated with this port in Simulink.
num tells the index to assign. Indexing starts with 1
(as in Simulink).
setType(typeName)
Sets the type of this port to type. Type must be one of
Bool, UFix_<n>_<b> , Xfix_<n>_<b> , signed or
unsigned. The last two choices leave the width and
binary point position unchanged.
setWidth(w)
Sets the width of this port to w.
setBinpt(bp)
Sets the binary point position of this port to bp.
makeBool()
Makes this port Boolean.
makeSigned()
Makes this port signed.
makeUnsigned()
Makes this port unsigned.
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Method
Description
setConstant()
Makes this port constant
setGatewayFileName(filename)
Sets the dat file name that will be used in simulations
and test-bench generation for this port. This function
is only meant for use with bi-directional ports so that
a hand written data file can be used during
simulation. Setting this parameter for input or
output ports is invalid and will be ignored.
setRate(rate)
Assigns the rate for this port. rate must be a positive
integer expressed as a MATLAB double or Inf for
constants.
useHDLVector(s)
Tells whether a 1-bit port is represented as single-bit
(ex: std_logic) or vector (ex: std_logic_vector(0
downto 0)).
HDLTypeIsVector()
Sets representation of the 1-bit port to
std_logic_vector(0 downto 0).
HDL Co-Simulation
Introduction
This topic describes how a mixed language/mixed flow design that includes Xilinx blocks,
HDL modules, and a Simulink block diagram can be simulated in its entirety.
System Generator simulates black boxes by automatically launching an HDL simulator,
generating additional HDL as needed (analogous to an HDL testbench), compiling HDL,
scheduling simulation events, and handling the exchange of data between the Simulink
and the HDL simulator. This is called HDL co-simulation.
Configuring the HDL Simulator
Black box HDL can be co-simulated with Simulink using the System Generator interface to
either ISE Simulator or the ModelSim simulation software from Model Technology, Inc.
ISE Simulator
To use the ISE Simulator for co-simulating the HDL associated with the black box, select
ISE Simulator as the option for the Simulation mode parameter on the black box as shown
in the following figure. The model is then ready to be simulated and the HDL cosimulation takes place automatically.
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ModelSim Simulator
To use the ModelSim simulator by Model Technology, Inc., you must first add the
ModelSim block that appears in the Tools library of the Xilinx Blockset to your Simulink
diagram.
For each black box that you wish to have co-simulated using ModelSim simulator, you
need to open its block parameterization dialog and set it to use the ModelSim session
represented by the black box that was just added. You do this by making the following two
settings:
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1. Change the Simulation Mode field from Inactive to External co-simulator.
2. Enter the name of the ModelSim block (e.g., ModelSim) in the HDL Co-Simulator to use
field.
The block parameter dialog for the ModelSim block includes some parameters that you
can use to control various options for the ModelSim session. See the Modelsim block help
pages for details. The model is then ready to be simulated with these options, and the HDL
co-simulation takes place automatically.
Co-Simulating Multiple Black Boxes
System Generator allows many black boxes to share a common ModelSim co-simulation
session. I.e., many black boxes can be set to "use" the same ModelSim block. In this case,
System Generator automatically combines all black box HDL components into a single
shared top-level co-simulation component. This is transparent to the user. It does mean,
however, that only one ModelSim simulation license is needed to co-simulate several black
boxes in the Simulink simulation.
For an example of how to do this, see Simulating Several Black Boxes Simultaneously.
Multiple black boxes can also be co-simulated with ISE Simulator by just selecting ISE
Simulator as the option for Simulation mode on each black box.
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Black Box Examples
Black Box Tutorial Example 1:
Importing a Core Generator
Module that Satisfies Black Box
HDL Requirements
Describes an approach that uses the System Generator
Black Box Configuration Wizard.
Black Box Tutorial Example 2:
Importing a Core Generator
Module that Needs a VHDL
Wrapper to Satisfy Black Box
HDL Requirements
Describes an approach that requires that you to
provide a VHDL core wrapper. Simulation issues are
also addressed.
Black Box Tutorial Example 3:
Importing a VHDL Module
Describes how to use the Black Box block to import
VHDL into a System Generator design and how to use
ModelSim to co-simulate.
Black Box Tutorial Example 4:
Importing a Verilog Module
Demonstrates how Verilog black boxes can be used in
System Generator and co-simulated using ModelSim.
Black Box Tutorial Example 5:
Dynamic Black Boxes
Demonstrates dynamic black boxes using a transpose
FIR filter black box that dynamically adjusts to
changes in the widths of its inputs.
Black Box Tutorial Example 6:
Simulating Several Black Boxes
Simultaneously
Demonstrates how several System Generator Black
Box Blocks can be co-simulated simultaneously, using
only one ModelSim license while doing so.
Black Box Tutorial Exercise 7:
Advanced Black Box Example
Using ModelSim
Describes how to design a Black Box block with a
dynamic port interface and how to configure a black
box using mask parameters. Also, describes how to
assign generic values based on input port data types
and how to save black box blocks in Simulink libraries
for later reuse. How to specify custom scripts for
ModelSim HDL co-simulation is also covered.
Importing a Xilinx Core Generator Module
This topic describes two different ways of importing Xilinx CORE Generator modules, as
black boxes, into System Generator. The first example shows how to import blocks which
satisfy Black Box HDL Requirements and Restrictions. The second example shows how to
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write a VHDL wrapper to import CORE generator modules as black boxes. The flow graph
below illustrates the process of importing CORE generator modules.
Black Box Tutorial Example 1: Importing a Core Generator Module that
Satisfies Black Box HDL Requirements
1.
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Start Core Generator and open the the following Core Generator project file:
./Xilinx/sysgen/examples/coregen_import/example1/coregen_import
_example1.cgp
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2.
Double click the CORDIC 3.0 icon to launch the customization GUI
3.
Parameterize and generate the CORDIC 3.0 core with component name
cordic_sincos, a functional Selection of Sin and Cos and the remaining options set
to be the default values as shown below:
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4.
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Click Generate. Core Generator produces the following files after generation:
♦
cordic_sincos.edn: Implementation netlist
♦
cordic_sincos.vhd: VHDL wrapper for behavioral simulation
♦
cordic_sincos.vho: Core instantiation template
♦
cordic_sincos.xco: Parameters selected for core generation
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5.
Start Simulink and open the design file
(./Xilinx/sysgen/examples/coregen_import/example1/coregen_impor
t_example1.mdl)
6.
Drag and drop the black box from the "Basic Elements" library into the model
coregen_import_example1.mdl. Select cordic_sincos.vhd for the top-level
HDL file.
7.
Connect the input and output ports of the black box to the open wires.
8.
Open the cordic_sincos_config.m file, and add the EDIF netlist to the black box
file list as shown below. This file will get included as part of the System Generator
netlist for the design when it is netlisted.
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Open the black box parameterization GUI and select ISE Simulator for the simulation
mode.
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10. Press the Simulate button to compile and co-simulate the CORDIC core using the ISE
simulator. The simulation results are as shown below.
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Black Box Tutorial Example 2: Importing a Core Generator Module that
Needs a VHDL Wrapper to Satisfy Black Box HDL Requirements
1.
Start Core Generator and open the Core Generator following project file:
./Xilinx/sysgen/examples/coregen_import/example2/coregen_import
_example2.cgp
2.
Double click the MAC FIR Filter 5.1 icon to launch the customization GUI.
3.
Customize and generate the MAC FIR Filter 5.1 core with the following parameters:
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Component Name: mac_fir_8tap
♦
Number of Taps: 8
♦
Impulse Response: Symmetric
♦
Load Coefficients: mac_fir_8tap.coe file located in sysgen directory
♦
System Clock Rate: 100 Mhz, Input rate: 25 Mhz
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♦
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Other parameters are set to default values.
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4.
Core Generator produces the following files after generation:
♦
mac_fir_8tap.edn: Implementation netlist
♦
mac_fir_8tap.vhd: VHDL wrapper for behavioral simulation
♦
mac_fir_8tap.vho: Core instantiation template
♦
mac_fir_8tap.xco: Parameters selected for core generation
♦
mac_fir_8tap.mif, DATA_COEF_BUFFER_A1.mif,
DATA_COEF_BUFFER_B1.mif: Memory initialization files for functional
simulation
5.
Since the MACFIR core does not have a ce port and the System Generator blackbox
requires a clk, ce pair, you will need to specify a core wrapper to add a ce port to the
top level.
6.
Open the following empty template wrapper file:
./Xilinx/sysgen/examples/coregen_import/example2/
mac_fir_8tap_wrapper.vhd
This file contains an empty entity declaration.
7.
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Modify the template wrapper according to the instructions below:
♦
Open the mac_fir_8tap.vho file.
♦
Copy the component declaration from mac_fir_8tap.vho and paste it in
mac_fir_8tap_wrapper.vhd in the component declaration area.
(after -- Add Component Declaration from VHO file ------)
♦
Copy the core instantiation template from mac_fir_8tap.vho and paste it in
mac_fir_8tap_wrapper.vhd in the architecture body.
(after ------------- ADD INSTANTIATION Template -----)
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♦
Copy the port declaration for the component mac_fir_8tap and paste it for the
mac_fir_8tap entity declaration
(after ---- Add Port declaration for entity ----)
♦
Add the ce port to the top-level entity declaration, and change the case of the CLK
port to clk.
Start Simulink and open the following design file:
<sysgen_tree>/examples/coregen_import/example2/coregen_import_e
xample2.mdl
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9.
Drag and drop the black box from the "Basic Elements" library in the
coregen_import_example2.mdl. Select mac_fir_8tap_wrapper.vhd for the
top-level HDL file.
10. Connect up the black box to the open wires.
11. Open the mac_fir_8tap_wrapper_config.m file, and add the VHDL file, EDIF
netlist and MIF files to the black box file list as shown below. These files get included
as part of the System Generator netlist for the design when it is generated.
Note: The order in which the files are added in the configuration function is the order in which they
get compiled during synthesis and simulation.
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12. Open the black box parameterization GUI and select the ISE Simulator for simulation
mode.
13. Press the Simulate button to compile and co-simulate the FIR core using the ISE
simulator. The simulation results are as shown below.
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Importing a VHDL Module
Black Box Tutorial Example 3: Importing a VHDL Module
This topic explains how to use the black box to import VHDL into a System Generator
design and how to use ModelSim to co-simulate the VHDL module.
1.
From the MATLAB console, change the directory to
<sysgen_tree>/examples/black_box/intro.
The following files are located in this directory:
2.
♦
black_box_intro.mdl - A Simulink model containing an example black box.
♦
transpose_fir.vhd - Top-level VHDL for a transpose form FIR filter. This file
is the VHDL that is associated with the black box.
♦
mac.vhd – Multiply and add component used to build the transpose FIR filter.
Open the black_box_intro model from the MATLAB command window by
typing
>> black_box_intro
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3.
Open the subsystem named Transpose FIR Filter Black Box. At this point, the
subsystem contains two inports and one outport. The black box subsystem is shown
below:
4.
Go to the Simulink Library Browser and add a black box block to this subsystem. The
black box is located in the Xilinx Blockset's Basic Elements library. The Black Box
Configuration Wizard is automatically invoked when a new black box is added to the
subsystem. A browser window appears that lists the VHDL source files that can be
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associated with the black box. From this window, select the top -level VHDL file
transpose_fir.vhd. This is illustrated in the figure below:
Note: The wizard will only run if the black box is added to a model that has been saved to a file. If
the model has not been saved, the wizard does not know where to search for files and System
Generator will instead display a warning that looks like the following:
5.
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The wizard parses the VHDL to generate a configuration M-function for the black box.
This is a MATLAB script that, among other things, associates the black box to the
VHDL and creates black box ports. Once the function has run, the ports on the black
box match those in the top-level VHDL entity (not including clock and clock enable
ports). This is illustrated below:
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Be aware of the following rules when working this example:
6.
♦
A synchronous HDL design that is associated with a black box must have one or
more clock and clock enable ports. These ports must occur in pairs, one clock for
each clock enable, and vice-versa. Each of these ports must be of type std_logic.
The name of the clock port must contain the substring clk. The name of the clock
enable port must be the same as the name of the clock port, but with ce
substituted for clk.
♦
The clock enable port has a specific meaning to System Generator and is not a
general purpose user enable for the block. Refer to the topic Black Box HDL
Requirements and Restrictions for details.
Double click on the black box block. The dialog box shown below appears:
The following are the fields in the dialog box:
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♦
Block configuration M-function - This specifies the name of the configuration Mfunction for the black box. In this example, the field contains the name of the
function that was generated by the Configuration Wizard. By default, the black
box uses the function the wizard produces. You can, however, substitute one you
produce yourself. For more information on the configuration M-function, refer to
the topic Black Box Configuration M-Function.
♦
Simulation mode - There are three simulation modes:
-
Inactive - When the mode is Inactive, the black box participates in the
simulation by ignoring its inputs and producing zeros. This setting is
typically used when a separate simulation model is available for the black
box, and the model is wired in parallel with the black box using a simulation
multiplexer. Black Box Tutorial Example 1: Importing a Core Generator
Module that Satisfies Black Box HDL Requirements shows how this is
accomplished.
-
ISE Simulator - When the mode is ISE Simulator, simulation results for the
black box are produced using co-simulation on the HDL associated to the
black box.
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-
♦
External co-simulator - When the mode is External co-simulator, it is
necessary to add a ModelSim HDL co-simulation block to the design, and to
specify the name of the ModelSim block in the field labeled HDL cosimulator to use. In this mode, the black box is simulated using HDL cosimulation.
FPGA Area Estimation - The numbers entered in this field are estimates of how
much of the FPGA is used by the HDL for the black box. These numbers must be
entered by hand. The numbers are only needed if you would like to use the
resource estimating utilities supplied with System Generator. For more
information, see Resource Estimation.
To continue the tutorial, leave the parameters set as they currently are.
7.
Wire the black box's ports to the corresponding subsystem ports.
8.
Run the simulation by clicking the Simulation Play button and then double click on the
scope block. Notice the black box output shown in the Output Signal scope is zero.
This is expected as the black box is configured to be inactive during simulation.
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9.
Go to the Simulink Library Browser and add a ModelSim block to this subsystem. The
ModelSim block is located in the Xilinx Blockset /Tools library. This block enables the
black box to communicate with a ModelSim simulator. Double click on the ModelSim
block to open the dialog box shown below:
10. Make sure the parameters match those shown in the preceding figure. Close the dialog
box.
11. From the Simulink menu, select Port Data Types from the Format menu to display the
port types for the black box. Compile the model (Ctrl-d) to ensure the port data types
are up to date. Notice that the black box port output type is UFix_26_0. This means it
is unsigned, 26 bits wide and has a binary point 0 positions to the left of the least
significant bit.
12. Open the configuration M-function transpose_fir_config.m and change the
output type from UFix_26_0 to Fix_26_12. The modified line should read:
dout_port.setType('Fix_26_12');
13. Edit the configuration M-function to associate an additional HDL file with the black
box. Locate the line:
this_block.addFile('transpose_fir.vhd');
Immediately above this line, add the following:
this_block.addFile('mac.vhd');
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14. Save the changes to the configuration M-function and recompile the model (Ctrl-d).
Your subsystem should appear as follows:
15. From the black box block parameter dialog box, change the Simulation mode field
from Inactive to External co-simulator. Enter ModelSim in the HDL co-simulator to
use field. The name in this field corresponds to the name of the ModelSim block that
you added to the model. The black box dialog box should appear as follows:
Note: Note: Only ModelSim XE and SE simulators are supported by System Generator.
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16. Run the simulation. A ModelSim command window and waveform viewer opens.
ModelSim simulates the VHDL while Simulink controls the overall simulation. The
resulting waveform looks something like the following:
The following warnings received in ModelSim can safely be ignored.
# ** Warning: There is an 'U'|'X'|'W'|'Z'|'-' in an arithmetic operand,
the result will be 'X'(es).
# Time: 0 ps Iteration: 0 Instance: /
xlcosim_black_box_ex1_down_converter_transpose_fir_filter_bl
ack_box_modelsim/
black_box_ex1_down_converter_transpose_fir_filter_black_box_
black_box/g0__22/g_last/m2
They are caused by the black box VHDL not specifying initial values at the start of
simulation.
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17. Examine the scope output after the simulation has completed. When the Simulation
Mode was set to Inactive, the Output Signal scope displayed constant zero. Notice the
waveform is no longer zero. Instead, Output Signal shows the results from the
ModelSim simulation.
Importing a Verilog Module
This example demonstrates how Verilog black boxes can be used in System Generator and
co-simulated using ModelSim. Verilog modules are imported the same way VHDL
modules are imported. For more information on how this is done, seethe topics Black Box
Configuration Wizard and Black Box Configuration M-Function. System Generator
provides all of the code that is needed to incorporate Verilog black boxes, both to generate
hardware and to co-simulate HDL. System Generator also allows Verilog black boxes to be
parameterized. This example demonstrates all of these capabilities. The files for this
example are contained in the following directory:
<sysgen_tree>/examples/black_box/example4.
The files are:
•
black_box_ex4.mdl – A Simulink model with two black boxes, one using VHDL
and the other using Verilog.
•
word_parity_block.vhd – The VHDL for the combinational portion of the state
machine seen in word parity example presented above. This is a purely combinational
(stateless) block that computes the parity of each input word and outputs the parity
bit. It has been parameterized with a generic so that it can accept any input type (see
the description of dynamic black boxes for a discussion of generics).
•
word_parity_block_config.m – The configuration M-function for the VHDL
black box, including the generic setting. The M-function tags this block as
combinational so that it simulates correctly in Simulink.
•
shutter.v – The Verilog for a simple synchronous latch. The code has been
parameterized so that the input port din can have arbitrary width.
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•
shutter_config.m – The configuration M-function for the Verilog black box,
including the parameter setting. The configuration M-function uses methods referring
to VHDL syntax even for configuring Verilog black boxes. Thus for this black box, you
have the lines:
this_block.setEntityName('shutter');
this_block.addGeneric('din_width', dwidth);
Black Box Tutorial Example 4: Importing a Verilog Module
1.
Navigate into the example4 directory and open the example model.
This is a simple design with two black boxes, one VHDL and the other Verilog. The
VHDL black box computes the parity of each input word, and the Verilog black box
latches the words that have odd parity. No Simulink model is used to compute the
behavior of the black boxes; instead, HDL co-simulation is used. The example model is
shown in the figure below.
You must have a license for mixed-mode ModelSim simulation to run this example. If
you do and you run the simulation, you will see a ModelSim waveform window that
looks like the one captured below. The behavior of both black boxes is shown. You can
browse the design structure in ModelSim to see how System Generator has combined
the two black boxes.
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2.
Change the input type to an arbitrary type and rerun the simulation. Both black boxes
adjust in the appropriate way to the change.
Dynamic Black Boxes
This example extends the transpose FIR filter black box so that it is dynamic, i.e., able to
adjust to changes in the widths of its inputs. The example is contained in the directory
<sysgen_tree>/examples/black_box/example3. For this example to run correctly,
you must change your directory (cd within the MATLAB command window) to this
directory before launching the example model.
The files contained in this directory are:
•
black_box_ex3.mdl - A Simulink model containing a dynamic black box.
•
transpose_fir_parametric.vhd – The VHDL for the transpose FIR filter.
•
mac.vhd – Multiply and add component used to build the transpose FIR filter.
•
transpose_fir_parametric_config.m – The configuration M-function for the
black box.
Black Box Tutorial Example 5: Dynamic Black Boxes
1.
Open the model by typing black_box_ex3 at the MATLAB command prompt.
2.
Run the simulation from the top-level model, and view the results displayed in the
scopes.
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3.
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Reduce the number of bits on the gateway Din Gateway In from 16 bits down to 12
and the binary point from 14 to 10, then run the simulation again. Note that both the
input and output widths on the black box adjust automatically. The black box
subsystem and simulation results should look like those shown below.
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4.
The black box is able to adjust to changes in input width because of its configuration
M-function. To make this work, the M-function must be augmented by hand. Open the
M-function file transpose_fir_parametric.m. The important points are described
below.
•
Obtaining data input width:
input_bitwidth = this_block.port('din').width;
•
Calculating output width:
output_bitwidth = ceil(log2(2^(input_bitwidth-1)*2^(coef_bitwidth-1) *
number_of_coef));
•
Setting output data type:
dout_port.makeSigned;
dout_port.width = output_bitwidth;
dout_port.binpt = 12;
•
Passing input and output bit widths to VHDL as generics:
this_block.addGeneric('input_bitwidth',this_block.port('din').width);
this_block.addGeneric('output_bitwidth',output_bitwidth);
For details concerning the black box configuration M-function, seethe topic Black Box
Configuration M-Function.
If you examine the black box VHDL file transpose_fir_parametric.vhd you see generics
input_bitwidth and output_bitwidth that specify input and output width. These
are passed to lower-level VHDL components.
Simulating Several Black Boxes Simultaneously
Several System Generator black boxes can co-simulate simultaneously, using only one
ModelSim license while doing so. The example shown below illustrates this. The files for
the example are contained in the directory
<sysgen_tree>/examples/black_box/example2.
The files contained in this directory are:
•
black_box_ex2.mdl: A Simulink model containing two black boxes.
•
parity_block.vhd: VHDL for a simple state machine that tracks the running
parity of an 8-bit input word.
•
parity_block_config.m: The configuration M-function for the black boxes. The
code has barely been changed from what was produced by the Configuration Wizard:
the line that tagged the block as having a combinational feed-through path
(this_block.tagAsCombinational) has been removed.
Black Box Tutorial Example 6: Simulating Several Black Boxes
Simultaneously
Navigate into the example2 directory and open the example model. This is a simple
model with two identical black boxes, each implementing a state machine. The state
machines compute the running parity of their inputs. One black box is fed the input stream
of the model and the other is fed the input stream after it has been serialized and deserialized. Notice that no simulation model is provided for either state machine. Instead,
HDL co-simulation is used to produce simulation results. The ModelSim block provides
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the connection between the black boxes and ModelSim. The example model is shown in
the figure below.
If you run the simulation, you will see a Simulink scope and ModelSim waveform window
that look like the figures below. The scope shows that the black boxes produce matching
parity results (as expected), but with one delayed from the other by one clock cycle. The
waveform window shows the same results, but viewed in ModelSim and expressed in
binary. System Generator automatically configures the waveform viewer to display the
input and output signals of each black box. You can also browse the design structure in
ModelSim to see how System Generator has elaborated the design to combine the two
black boxes.
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Advanced Black Box Example Using ModelSim
The following topics are discussed in this example:
•
How to design a black box with a dynamic port interface;
•
How to configure a black box using mask parameters;
•
How to assign generic values based on input port data types;
•
Saving black box blocks in Simulink libraries for later reuse;
•
How to specify custom scripts for ModelSim HDL co-simulation.
This example also shows a way to view signals coming from a black box. In Simulink,
waveforms are typically viewed with a scope. The Simulink scope block serves this
purpose and the System Generator WaveScope block is available in versions 8.1 and later.
The waveform viewer in the ModelSim simulator may also be used to view waveforms. In
this example, a black box is configured as a specialized ModelSim waveform scope for
Xilinx fixed-point signals. When a model that uses the black box scope is simulated, the
signals that drive the black box are displayed in ModelSim.
The files for this example are contained in the directory
<sysgen_tree>/examples/black_box/example5.
The files contained in this directory are:
•
black_box_ex5.mdl: A Simulink model containing a black box scope.
•
scope_lib.mdl: A Simulink library containing the black box waveform viewer.
•
scope_config.m: The configuration M-function for the black box waveform viewer.
•
scope1.vhd, scope2.vhd, scope3.vhd, scope4.vhd: Black box VHDL for the
signal scope that accept one, two three, and four input signals, respectively.
•
waveform.do – A script that instructs ModelSim how to display signals during
simulation.
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Black Box Tutorial Exercise 7: Advanced Black Box Example Using
ModelSim
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1.
Navigate into the example5 directory and open the example black_box_ex5.mdl file.
The model includes an adder that is driven by two input gateways. The gateways are
configured to produce signed 8-bit values, each with six bits to the right of the binary
point. Sine wave generators drive the gateways. The model also includes a black box
named waveform scope. This is driven by three signals. The first input is driven by the
adder. The other two are driven by the inputs to the adder. The ModelSim block
enables HDL co-simulation. The example model is shown below.
2.
Simulate the black_box_ex5 model. A ModelSim window opens and ModelSim
compiles the files necessary for simulation. After the compilation is complete, both
MATLAB and ModelSim simulations begin. A ModelSim waveform viewer opens and
displays four signals. The first input to the block, sig1, is driven by the adder. This
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signal is represented in two ways in the ModelSim viewer – binary and analog. The
ModelSim waveforms for the black_box_ex5 simulation are shown below.
3.
Double click on the Simulink scope in the model. The output is shown below and
resembles the analog signal in the ModelSim waveform viewer.
The black box in this example is configured using mask parameters. There are many
situations in which this is useful. In this case, the number of black box input ports, i.e.,
the number of scope inputs, is determined by a mask parameter.
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4.
Double click on the waveform scope black box. Notice a Number of Input Ports field is
included in the block dialog box and is unique to this black box instance. The dialog
box is shown below:
5.
Change the number of input ports from 3 to 4 and apply the changes. The black box
now has an additional input port labeled sig4 and should look like the following:
Every black box has a standard list of mask parameters. The black box in this example
has an additional mask parameter nports that stores the number of input ports
selected by the user. To change a black box mask it is necessary to disable the link to the
library. When a black box is changed in this way, it is best to save the black box in a
library. (See the Simulink documentation on libraries for details.) The tutorial library
scope_lib.mdl contains the modified signal scope black box used in this example.
When a black box configuration M-function adds an HDL file, the path to the file can
be relative to the directory in which the library is saved. This eliminates the need to
copy the HDL into the same directory as the model.
The black box's configuration M-function is invoked whenever the block parameter
dialog box is modified. This allows the M-function to check the mask parameters and
configure the black box accordingly. In this example, the M-function adjusts the
number of block input ports based on the nports parameter specified in the mask.
6.
Open the file scope_config.m that defines the configuration M-function for the
example black box. Locate the line:
simulink_block = this_block.blockName;
This obtains the Simulink name of the black box and assigns it to the variable
simulink_block. The name is useful because it is the handle that MATLAB
functions need to manipulate the block.
7.
Locate the line:
nports = eval(get_param(simulink_block,'nports'));
The value of the nports mask parameter is obtained by the get_param command.
The get_param returns a string containing the number of ports. An eval encloses the
get_param and converts the string into an integer that is assigned to the nports
variable.
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8.
Once the number of input ports is determined, the M-function adds the input ports to
the black box. The code that does this is shown below.
for i=1:nports
this_block.addSimulinkInport(sprintf('sig%d',i));
end
There are four VHDL files, named scope1.vhd, scope2.vhd, scope3.vhd, and
scope4.vhd, which the black box in this example can use. The black box associates
itself to the one that declares an appropriate number of ports.
9.
The configuration M-function selects the appropriate VHDL file for the black box.
Locate the following line in scope_config.m:
entityName = sprintf('scope%d',nports);
The HDL entity name for the black box is constructed by appending the value of
nports to scope. The VHDL is associated with the black box in the following line:
this_block.addFile(['vhdl/' entityName '.vhd']);
10. The input port widths for each VHDL entity are assigned using generics. The generic
name identifies the input port to which the width is assigned. For example, the width3
generic specifies the width of the third input. In scope_config.m, the generic names
and values are set as follows:
% ----------------------------if (this_block.inputTypesKnown)
for i=1:nports
width = this_block.inport(i).width;
this_block.addGeneric(sprintf('width%d',i),width);
end
end % if(inputTypesKnown)
% -----------------------------
11. You can change the way ModelSim displays the signal waveforms during simulation
by using custom tcl scripts in the ModelSim block. Double click on the ModelSim block
in the black_box_ex5 model. The following dialog box appears:
Custom scripts are defined by selecting the Add Custom Scripts checkbox. In this
case, a script named waveform.do is specified in the Script to Run after vsim field.
This script contains the ModelSim commands necessary to display the adder output as
an analog waveform.
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Chapter 5
System Generator Compilation Types
There are different ways in which System Generator can compile your design into an
equivalent, often lower-level, representation. The way in which a design is compiled
depends on settings in the System Generator dialog box. The support of different
compilation types provides you the freedom to choose a suitable representation for your
design’s environment. For example, an HDL or NGC netlist is an appropriate
representation when your design is used as a component in a larger system. If, on the other
hand, the complete system is modeled inside System Generator, you may choose to
compile your design into an FPGA configuration bitstream. Sometimes you may want to
compile your design into an equivalent high-level module that performs a specific
function in applications external to System Generator (e.g., ModelSim hardware cosimulation).
HDL Netlist Compilation
System Generator uses the HDL Netlist compilation
type as the default generation target. More details
regarding the HDL Netlist compilation flow can be
found in the topic Compilation Results.
NGC Netlist Compilation
Describes how System Generator can be configured to
compile your design into a standalone NGC file.
Bitstream Compilation
Describes how System Generator can be configured to
compile your design into an FPGA configuration
bitstream.
EDK Export Tool
Describes how System Generator can be configured to
compile your design into an FPGA configuration
bitstream that is appropriate for the selected part.
Hardware Co-Simulation
Compilation
Describes how System Generator can be configured to
compile your design into FPGA hardware that can be
used by Simulink and ModelSim.
Timing Analysis Compilation
Describes how to use the System Generator Timing
Analysis tool compilation target.
Creating Compilation Targets
Describes how to add custom compilation targets to
the System Generator block.
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HDL Netlist Compilation
System Generator uses the HDL Netlist compilation type as the default generation target.
More details regarding the HDL Netlist compilation flow can be found in the sub-topic
titled Compilation Results.
As shown below, you may select HDL netlist compilation by left-clicking the Compilation
submenu control on the System Generator block dialog box, and select the HDL Netlist
target.
NGC Netlist Compilation
The NGC Netlist compilation target allows you to compile your design into a standalone
Xilinx NGC binary netlist file. The NGC netlist file that System Generator produces
contains the logical and optional constraint information for your design. This means the
HDL, cores, and constraints file information corresponding to a System Generator design
are self-contained within a single file.
If you have chosen to include clock wrapper logic in your design, the netlist file is saved as
<design>_cw.ngc. Otherwise, the file is saved as <design>.ngc. Here <design> is
derived from the portion of the design being compiled. This file can be used as a module in
a larger design, or as input to NGDBuild when the netlist constitutes the complete design.
For an example showing how a System Generator design can be used as a component in a
larger design, refer to the topic titled Importing a System Generator Design into a Bigger
System.
The NGC compilation target generates an HDL component instantiation template that
makes it easy to include your System Generator design as a component in a larger design.
For VHDL compilation, the template is saved as <design>_cw.vho when the clock
wrapper is included. Otherwise it is saved as <design>.vho . Alternatively, a .veo
extension is used for Verilog compilation. The instantiation template is saved in the
design's target directory.
System Generator produces the NGC netlist file by performing the following steps during
compilation:
1.
Generates an HDL netlist for the design;
2.
Runs the selected synthesis tool to produce a lower-level netlist. The type of netlist
(e.g., EDIF for Synplify or Synplify Pro, NGC for XST) depends on which synthesis tool
is chosen for compilation.
Note: Note: IO buffers are not inserted in the design during synthesis.
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3.
Combines synthesis results, core netlists, black box netlists, and optionally the
constraints files into a single NGC file.
As shown below, you may select the NGC compilation target by left-clicking the
Compilation submenu control on the System Generator block dialog box, and selecting the
NGC Netlist target.
You may access additional compilation settings specific to NGC Netlist compilation by
clicking on the Settings... button when NGC Netlist is selected as the compilation type in
the System Generator block dialog box. Parameters specific to the NGC Netlist Settings
dialog box include:
•
Include Clock Wrapper: Selecting this checkbox tells System Generator whether the
clock wrapper portion of your design should be included in the NGC netlist file. Refer
to the topic Compilation Results for more information on the clock wrapper.
Note: If you exclude the clock wrapper from multirate designs, you will need to drive the clock
enable ports with appropriate signals from your own top-level design.
•
Include Constraints File: Selecting this checkbox tells System Generator whether the
constraints file associated with the design should be included in the NGC netlist file.
Note: When the constraints file is excluded, you should supply your own constraints to ensure
the multi-cycle paths in the System Generator design are appropriately constrained.
Bitstream Compilation
The Bitstream compilation type allows you to compile your design into a Xilinx
configuration bitstream file that is suitable for the FPGA part that is selected in the System
Generator dialog box. The bitstream file is named <design>_cw.bit and is placed in the
design's target directory, where <design> is derived from the portion of the design being
compiled.
System Generator produces the bitstream file by performing the following steps during
compilation:
1.
Generates an HDL netlist for the design;
2.
Runs the selected synthesis tool to produce a lower-level netlist. The type of netlist
(e.g., EDIF for Synplify Pro, NGC for XST) depends on which synthesis tool is chosen
for compilation.
3.
Runs XFLOW to produce a configuration bitstream.
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As shown below, you may select the Bitstream compilation by left-clicking the
Compilation submenu control on the System Generator block dialog box, and selecting the
Bitstream target.
System Generator uses XFLOW to run the tools necessary to produce the configuration
bitstream. Execution of XFLOW is broken into two flows, implementation and configuration.
The implementation flow is responsible for compiling the synthesis tool netlist output
(e.g., EDIF or NGC) into a placed and routed NCD file. In summary, the implementation
flow performs the following tasks:
1.
Combines synthesis results, core netlists, black box netlists, and constraints files using
NGDBuild.
2.
Runs MAP, PAR, and Trace on the design (in that particular order).
The configuration flow type runs the tools (e.g., BitGen) necessary to create an FPGA BIT
file, using the fully elaborated NCD file as input.
XFLOW Option Files
The implementation and configuration flow types have separate XFLOW options files
associated with them. An XFLOW options file declares the programs that should be run for
a particular flow, and defines the command line options that are used by these tools. The
Xilinx ISE software includes several example XFLOW options files. From the base
directory of your Xilinx ISE software tree (e.g., c:\Xilinx\), these files are located under the
xilinx\data directory (e.g., C:\Xilinx\xilinx\data). Three commonly used implementation
options files include:
•
balanced.opt;
•
fast_runtime.opt;
•
high_effort.opt.
Note: By default, System Generator uses the balanced.opt file for the implementation flow, and
bitgen.opt file for the configuration flow.
Sometimes you may want to use options files that use settings that differ (e.g., to specify a
higher placer effort level in PAR) from the default options provided by the target. In this
case, you may create your own options files, or edit the default options files to include your
desired settings. The Bitstream settings dialog box allows you to specify options files other
than the default files.
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Additional Settings
You may access additional compilation settings specific to Bitstream compilation by
clicking on the Settings... button when Bitstream is selected as the compilation type in the
System Generator block dialog box. Parameters specific to the Bitstream Settings dialog
box include:
•
•
Import Top-level Netlist: Allows you to specify your own top-level netlist into which
the System Generator portion of the design is included as a module. You may choose
to import your own top-level netlist if you have a larger design that instantiates the
System Generator clock wrapper level as a component. Refer to the Compilation
Results topic for more information on the clock wrapper level. This top-level netlist is
included in the bitstream file that is generated during compilation. Selecting this
checkbox enables the edit fields Top-level Netlist File (EDIF or NGC) and Search Path
for Additional Netlist and Constraint Files.
♦
Top-level Netlist File (EDIF or NGC): Specifies the name and location of the toplevel netlist file to include during compilation. Note that any HDL components
that are used by your top-level (including the top-level itself) must have been
previously synthesized into netlist files.
♦
Search Path for Additional Netlist and Constraint Files: Specifies the directory
where System Generator should look for additional netlist and constraint files
that go along with the top-level netlist file. System Generator copies all netlist
(e.g., .edn, .edf, .ngc) and constraints files (e.g., .ucf, .xcf, .ncf) into the
implementation directory when this directory is specified. If you do not specify a
directory, System Generator will only copy the netlist file specified in the Toplevel Netlist File field.
Specify Alternate Clock Wrapper: Allows you to substitute your own clock wrapper
logic in place of the clock wrapper HDL System Generator produces. The clock
wrapper level is the top-level HDL file that is created for a System Generator design,
and is responsible for driving the clock and clock enable signals in that design.
Sometimes you may want to supply your own clock wrapper, for example, if your
design uses multiple clock signals, or if you have a board-specific hardware you
would like your design to interface to.
Note: The name of the alternate clock wrapper file must be named <design>_cw.vhd or
<design>_cw.v or it will not be used during bitstream generation.
•
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XFLOW Option Files: When a design is compiled for System Generator hardware cosimulation, the command line tool, XFLOW, is used to implement and configure your
design for the selected FPGA platform. XFLOW defines various flows that determine
the sequence of programs that should be run on your design during compilation.
There are typically multiple flows that must be run in order to achieve the desired
output results, which in the case of hardware co-simulation targets, is a configuration
bitstream.
♦
Implementation Phase (NBDBuild, MAP, PAR, TRACE): Specifies the options
file that is used by the implement flow type. By default, System Generator will
use the implement options file that is specified by the compilation target.
♦
Configuration Phase (BitGen): Specifies the options file that is used by the
configuration flow type. By default, System Generator will use the configuration
options file that is specified by the compilation target.
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Re-Compiling EDK Processor Block Software Programs in Bitstreams
When you perform bitstream compilation on a System Generator design with an EDK
Processor block, the imported EDK project and the shared memories sitting between the
System Generator design and MicroBlaze processor are netlisted and included in the
resulting bitstream.
System Generator also tries to compile any active software programs inside the imported
EDK project. If the compilation of active software programs succeeds, System Generator
invokes the data2bram utility to include the compiled software programs into the resulting
bitstream.
Note: No error or warning message is issued when System Generator encounters failures during
software program compilation or when System Generator updates the resulting bitstream with the
compiled software programs.
You can modify the software programs in the imported EDK project and use the following
command to compile the software programs, and update the System Generator bitstream
with the compiled software programs:
xlProcBlockCallbacks('updatebitstream', [], xmp_file, bit_file, bmm_file);
where
xmp_file is the pathname to the imported EDK project file
bit_file is the pathname to the Sysgen bitstream file
bmm_file is the pathname of the back-annotated BMM file produced by Sysgen during bitstream
compilation
If the imported EDK project contains a BMM file named imported_edk_project.bmm,
System Generator creates a back-annotated BMM file named
imported_edk_project_bd.bmm. You should provide the later back-annotated BMM
file to the above command in order to update the bitstream properly.
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EDK Export Tool
EDK Export Tool
The EDK Export Tool allows a System Generator design to be exported to a Xilinx
Embedded Development Kit (EDK) project. The EDK Export Tool simplifies the process of
creating a peripheral by automatically generating the files required by the EDK.
The EDK Export Tool can be accessed from the System Generator block GUI under the
Compilation pull-down menu – the figure below shows this being done. After the EDK
Export Tool is selected, the Settings… button will be enabled.
Clicking on the Settings… button brings up the EDK export settings dialog.
Pcore options allow you to do the following:
•
Assign a version number to your pcore
•
Select Pcore under development
This feature works for both FSL- and PLB-based pcore export. When a pcore is marked
as Pcore under development, XPS will not cache the HDL produced for this pcore.
This is useful when you are developing pcores in System Generator and testing them
out in XPS. You can just enable this checkbox, make changes in System Generator and
compiled in XPS. XPS always compiles the generated pcore, so you don’t have to
empty the XPS cache which may contain caches of other peripherals, thus slowing
down the compile of the final bitstream.
•
Select Enable custom bus interfaces
This feature works for both FSL- and PLB-based pcore export and allows you to create
custom bus interfaces that will be understood in XPS.
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Creating a Custom Bus Interface for Pcore Export
Consider the following example. In the model below, you have one design that you are
going to export as a pcore to XPS. This design has the output ports Pixel Enable, Y, Cr, and
Cb. You want to group these signals into a bus to simplify the connection in XPS.
2. Select
3. Click
1. Double Click
4. Select
5. Click
6. Enter Data
You follow the sequence in the figure above to bring up the Bus Interface dialog box. In
this dialog box, you define a new Bus Interface called vid_out that is marked as a
myVideoBus Bus Standard and is Bus Type INITIATOR. (Other supported Bus Types
include: Target, Master, Slave, Master-slave, Monitor.) Next, in the Port-Bus Mapping
table, you list all the gateways that you want in the bus, then give each a Bus Interface
Name. You then Netlist the design as a pcore. Remember that you marked this pcore bus as
INITIATOR since it contains outputs.
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In another model (shown below), you create corresponding input gateways. You set this
up as a TARGET bus giving the bus interface the same Bus Standard myVideoBus. XPS
will use the Bus Standard name to match different bus interfaces. XPS will then connect the
outputs to the inputs with the same Bus Interface Names.
You export this pcore to the XPS project. When these two pcores are used in the same XPS
project, XPS will detect that they have compatible buses and will allow you to connect
them if you wish.
Export as Pcore to EDK
When a System Generator design is exported to the EDK, the name of the pcore (processor
core) has the postfix "_plbw" appended to the model name if a PLB v6.4 bus is specified.
For example, when a model called mul_accumulate is exported to the EDK, it will be called
mul_accumulate_plbw on the EDK side. If Fast Simplex Link is specified, the postfix
“_sm” is appended to the model name.
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The following table shows subdirectory structure of the pcore that is generated by System
Generator:
pcore
Description
Subdirectory
data
The data directory contains four files: BBD, PAO, MPD and
TCL.
• The BBD (black-box definition) file tells the EDK what EDN
or NGC files are used in the design.
• The PAO (peripheral analyze order) file tells the EDK the
analyze order of the HDL files.
• The MPD (Microprocessor Peripheral Description) file tells
the EDK how the peripheral will connect to the processor.
• The TCL file is used by LibGen when elaborating software
drivers for this peripheral.
doc
Documentation files in HTML format.
hdl
The hdl directory contains the hdl files produced by System
Generator.
netlist
The netlist directory contains the EDN and NGC files listed by
the BBD file
src
Source files for the software drivers.
System Generator Ports as Top-Level Ports in EDK
Input and output ports created in System Generator are made available to the EDK tool as
ports on the peripheral. You may pull these ports to the top-level of the EDK design. This
is useful for instance when the System Generator design has ports that go to the
input/output pads on the FPGA device.
Supported Processors and Current Limitations
Currently, PLB v4.6 memory-map links and FSL memory-map links to the MicroBlaze
processor are exported with the EDK Export Tool. There can only be one instance of an
EDK Processor block.
See Also:
EDK Processor
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Hardware Co-Simulation Compilation
Hardware Co-Simulation Compilation
System Generator can compile designs into FPGA hardware that can be used in the loop
with Simulink simulations. This capability is discussed in the topic Using Hardware CoSimulation.
You may select a hardware co-simulation target by left-clicking the Compilation submenu
control on the System Generator dialog box, and selecting the desired hardware cosimulation platform. The list of available co-simulation platforms depends on which
hardware co-simulation plugins are installed on your system.
Note: If you have an FPGA platform that is not listed as a compilation target, you may create a new
System Generator compilation target that uses JTAG to communicate with the FPGA hardware. Refer
to the Supporting New Platforms for more information on how to do this.
Timing Analysis Compilation
Sometimes the hardware created by System Generator may not meet the requested timing
requirements. System Generator provides a Timing Analysis tool that can help you resolve
timing related issues. The timing analysis tool shows you, both in graphical and textual
formats, the slowest system paths and those paths that are failing to meet the timing
requirements. This allows you to concentrate on methods of speeding up those paths.
Methods for doing so will be discussed. Underlying the System Generator Timing Analysis
tool is Trace, a software application delivered as part of the ISE tool suite used to analyze
timing paths.
As shown below, you invoke the Timing Analyzer by double-clicking on the System
Generator block and selecting the Timing Analysis option from the Compilation
submenu. Specify the Part as you desired. It is important to choose the exact part you wish
to target as the size and speed of the part will affect the path delays. Result files will be put
in the Target Directory. The value in the FPGA Clock Period box is the value that will be
used during place & route:
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After filling out the dialog box, click the Generate button and System Generator will
perform the following steps:
1.
The design is compiled using Simulink.
2.
The design is netlisted by System Generator into HDL source.
3.
The HDL Synthesis Tool is called to turn the HDL into an EDIF (Synplify/Synplify
Pro) or NGC (XST) netlist.
4.
NGD Build is called to turn the netlist into an NGD netlist file.
5.
The ISE Mapper software is called to map elements of logic together into slices; this
creates an NCD file.
6.
The ISE Place & Route software is called to place the slices and other elements on the
Xilinx die and to route the connections between the slices. This creates another NCD
file.
7.
The ISE Trace software is called to analyze the NCD and to find the paths with the
worst slack. This creates a trace report.
8.
The System Generator Timing Analyzer tool appears, displaying the data from the
trace report.
Note: If timing data is generated using this method and you wish to view it again at a later time, then
enter the following command at the MATLAB command line:
>>xlTimingAnalysis('timing')
where 'timing' is the name of the target directory in which a prior analysis was carried out.
Timing Analysis Concepts Review
This brief topic is intended for those with little or no knowledge of logic path analysis.
Period and Slack
A timing failure usually means there is a setup time violation in the design. A setup time
violation means that a particular signal cannot get from the output of one synchronous
element to the input of another synchronous element within the requested clock period
and subject to the second synchronous element's setup time requirement. A typical path is
shown in this Synplify schematic:
The path shown is from the Q output of the register on the left (register3) to the D input of
the register on the right (parity_reg). The path goes through two LUTs (lookup tables) that
are configured as 4-input XOR gates. This path has two levels of logic. That means that it
goes through two separate combinational elements (the two LUTs).
The requested period for this path is 10ns. This path easily meets timing. The second of the
two red comma-separated numbers above each logic elements shows the slack for the path.
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The slack is the amount of time by which the path 'meets timing'. In this case the slack is
7.79ns. That means that the path could be 7.79ns slower and still meet the 10ns period
requirement. A negative slack value indicates that the path does not meet timing and has
a setup (or hold) time violation.
Path Analysis Example
Let us examine this path in more detail. The first value on the top of register3 is 0.35ns. This
means that the clk-to-out time of the register is 0.35ns, so the data will appear on the Q
output 0.35ns after the rising edge of the clock signal. (The clock signal, not shown, drives
the C inputs of both registers.)
The input of the LUT y_4[0] shows two numbers on each input. The first is the arrival time
of the signal. This value is 0.98ns. This means that the signal arrives at the input 0.98ns
after the rising edge of the clock. Therefore the net delay is (0.98ns-0.35ns)=0.63ns. Any
path delay is divided into net delays and logic delays. In an FPGA, the net delays are
normally the predominant type of delay. This is because the configurable routing fabric of
the FPGA requires that a net traverse many delay-inducing switchboxes in order to reach
its destination.
The path leaves y_4[0] and travels along another net to y[0]. The first of the two values at
the output of y[0] shows the arrival time of the signal at the output of that LUT. This value
is 1.62ns. The signal travels along the final net, incurring a net delay of 0.26ns to arrive at
the D input of parity_reg at 1.88ns after the clock edge. This register has a required setup
time. The setup time for this register is 0.33ns. This means that the signal must arrive at the
D input 0.33ns before the rising edge of the next clock. Therefore the total path requires
(1.88ns+0.33ns)=2.21ns. Subtracted from 10ns, this yields the 7.79ns slack value.
Clock Skew and Jitter
The net delay values shown here are estimates provided by Synplify. The synthesizer
doesn't know the actual net delay values because these are not determined until after the
place & route process. An actual path contains other variables which must be accounted
for, including clock skew and clock jitter. Clock skew is the amount of time between clock
arrival at the source and destination synchronous elements. Clock jitter is a variation of the
clock period from cycle to cycle. Jitter is created by the DCMs (digital clock managers) and
by other means. The timing analysis is carried out with worst-case values for the given
part's delay values, jitter, skew, and temperature derating.
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Timing Analyzer Features
Observing the Slow Paths
Clicking on the Slow Paths icon displays the paths with the least slack for each timing
constraint. An example is shown below:
The top section of the display shows a list of slow paths, while the bottom section of the
display shows details of the path that is selected. The elements of this display are explained
here:
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•
Timing Constraint: You may opt to view the paths from all timing constraints or just a
single constraint. A typical System Generator design has but a single timing
constraint which defines the period of the system clock. This is the constraint shown
in this example. TS_clk_a5c9593d is the name of the constraint; the (sometimes
confusing) suffix is a hash meant to make the identifier unique when multiple System
Generator designs are used as components inside a larger design. The timing group
clk_a5c9593 is a group of synchronous logic, again with a hash suffix. The group in
this case contains all the synchronous elements in the design. The period of the clock
here is 10ns with a 50% duty cycle.
•
Source: The System Generator block that drives the path.
•
Destination: This is the System Generator block that is the terminus of the path.
•
Slack: The slack for this particular path. See the topic entitled Period and Slack for
more details.
•
Delay (Path): The delay of the entire path, including the setup time requirement.
•
% Route Delay: This is the percentage of the path that is consumed by routing (net)
delay. The remainder portion of the path is consumed by logic delay.
•
Levels of Logic: The number of levels of combinatorial logic in the path. The
combinatorial logic typically comprises LUTs, F5 muxes, and carry chain muxes.
•
Path Element: This shows the logic and net elements in the highlighted path.
•
Delay (Element): This shows the delay through the logic and net elements in the
highlighted path.
•
Type of Delay: This is the kind of delay incurred by the given path element. These
values are defined in the Xilinx part's data sheet. In the example shown above, Tcko is
the clk-to-out time of a flip-flop; net is a net delay; Tilo is the delay through a LUT, and
Tas is the setup time of a flip-flop.
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You may click on the column headings to reorder the paths or elements according to delay,
slack, path name, or other column headings. Failing paths are highlighted in red/pink.
Name Unmunging and Displaying Low-Level Names
Part of the magic of the timing analyzer lies in its ability to perform the un-glorious task of
name unmunging, the task of automatically correlating System Generator components with
the low-level component names produced by the Xilinx implementation tools. The names
of these components often differ considerably. In fact, the logic blocks and wires that
appear in a System Generator diagram may have only a loose relation to the actual logic
that gets generated during the synthesis process. The System Generator timing analyzer
must correlate the names of logic elements and nets in the trace report to blocks and wires
in the System Generator diagram.
The timing analyzer cannot always perform this un-munging process. In the path shown in
the screen capture above, path elements #2 and #5 have a question mark displayed in the
name field. This means that the timing analyzer could not un-munge the name from the
trace report and correlate it to a System Generator block.
To see the actual names from the trace report, check the Display low-level names box. This
will show the trace report names. You may be able to correlate them to System Generator
elements by observation.
Cross-Probing
Highlighting a path in the Slow Paths view will highlight the blocks in the path in the
System Generator diagram. The path's source and destination blocks, as well as
combinational blocks through which the path passes, will be highlighted in red. The
diagram below shows how the model appears when the path that has Registerc as its
source and parity_reg as its destination is highlighted. The blocks xor_1b, xor_2a, and
xor_3a are also highlighted because they are part of the path.
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Histogram Charts
Clicking on the Charts icon displays a histogram of the slow paths. This histogram is a
useful metric in analyzing the design. You may know that the design will only run at, for
example, 99MHz in your part when you wish it to run at 100MHz. But how close is the
design to meeting timing and how much work is involved in meeting this requirement?
The histogram will quickly give you an estimate of the work involved. For example, look
at the histogram of the results of a simple design below:
This shows that most of the slow paths are concentrated about 1.5ns. The slowest path is
about 2.35ns. The numbers at the tops of the bins show the number of paths in each bin.
There is only one path in the bin which encompasses the time range 2.31ns-2.39ns. The bins
to the right of it are empty. This shows that the slowest path is an outlier and that if your
timing requirement were for a period of, for example, 2ns, you would need only to speed
up this single path to meet your timing requirements.
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Histogram Detail
The slider bar allows you to adjust the width of the bins in the histogram. This allows you
to get more detail about the paths if desired. The display below shows the results of a
different design with a larger number of bins than the diagram above:
This diagram shows the paths grouped into three regions, with each forming a rough bell
curve distribution. These groups are probably from different portions of the circuit or from
different timing constraints that are from different clock regions. If you wish to analyze the
paths from a single timing constraint, you may select a single constraint for viewing from
the Timing constraint pulldown menu at the top of the display.
Note the bins and portions thereof shown in red. These are the paths that have negative
slack; i.e., they do not meet the timing constraint. In this example you can see that some
paths have failed but not by a large margin so it seems reasonable that with some work this
design could be reworked to meet timing.
Statistics
Clicking on the Statistics icon displays several design statistics, including the number of
constraints, paths analyzed, and maximum frequency of the design.
Trace Report
Clicking on the Trace icon shows the raw text report from the Trace program. This file gives
considerable detail about the paths analyzed. Each path analyzed contains information
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about every net and logic delay, clock skew, and clock uncertainty. The box at the bottom
left of this display shows the path name of the timing report.
Improving Failing Paths
"Now I have information about my failing paths; but what do I do now?" you may ask
yourself. This is the trick for which there is no simple answer, and this is where you may
need to delve into the lower-level aspects of FPGA design.
In general, steps that may be taken to meet timing are, in this order:
1.
Change the source design. Just about any timing problem can be solved by changing
the source design and this is the easiest way to speed up the circuit. Unfortunately, this
is often the last step taken by designers, who often look for a quick solution such as
using a faster part. The source design may be changed in several ways:
a.
Pipelining. This is the surest way to improve speed, but may also be tricky.
Adding pipelining registers increases latency. For designs with feedback, this may
require great care since portions of the design may require pipeline rebalancing.
See the later example for more details on pipelining.
b.
Parallelization. This is probably the second most-important improvement you can
make. Do you have a FIR filter that won't operate at the correct speed? You can use
two FIR filters in parallel, each operating at half-rate, and interleave the outputs.
This is the classic speed/area tradeoff.
c.
Retiming. This involves taking existing registers and moving them to different
points within the combinational logic to rob from Peter to pay Paul, so to speak.
This works if, to stretch the maxim, Paul is bereft of slack, while Peter has a surfeit.
Some synthesis tools can perform a degree of retiming automatically.
d. Replication. Replication of registers or buffers increases the amount of logic but
reduces the fanout on the replicated objects. This decreases the capacitance of the
net and reduces net delay. The replicated registers may also be floorplanned to
place them closer to the logic groups they drive. Replication is often performed
automatically by the tools and manual replication is not a common practice in a
high-level design environment like System Generator.
e.
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Shannon Expansion. This method involves replicating the faster logic in a critical
path in order to remove dependencies on slower logic. This is sometimes done
automatically by the synthesizer.
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f.
Using Hard Cores. Are you using a ROM that is implemented in distributed RAM
when it would operate much faster in a block memory hard core? Do you have a
wide adder that would benefit from being put in a DSP48 block, which can operate
at 500MHz? Take advantage of the embedded hard cores.
g.
New Paradigms. Do you need to create a large delay? Instead of using a counter
with a long carry chain, why not build a delay out of cascaded Johnson rings using
SRL16s? Or how about using an LFSR? Neither requires a carry chain and can
operate much faster. Sometimes you have to rethink certain design elements
completely.
2.
Eliminate overconstraints. Ensure that elements of your design that only need to be
operated at a subsampled rate are designed that way by using the downsample and
upsample blocks in System Generator. If these blocks are not used, then the timing
analyzer is not aware that these sections of the circuit are subsampled, and the design
is overconstrainted.
3.
Change the constraints. Is it possible to run the design at a lower clock speed? If so,
this is an easy way to meet your requirements. Unfortunately, this is rarely possible
due to design requirements.
4.
Increase PAR effort levels. The mapper and place & route tools (PAR) in ISE take
effort levels as arguments. When using ISE (from the Project Navigator GUI), try the –
timing option in MAP. You may also increase the PAR effort levels which will increase
the PAR execution time but may also result in a faster design.
5.
Multipass PAR. PAR is an iterative process and is somewhat chaotic in that the initial
conditions can vastly influence the final result. PAR uses a seed value to determine the
initial conditions. This is referred to as the cost table value. You may change this value
in the Project Navigator by hand. Even better, you may perform a multipass PAR
process which runs PAR multiple times with different cost table values. This is timeconsuming but often effective.
6.
Floorplanning. This step should be avoided if possible, but can yield huge
improvements. The automatic placer in PAR can be improved upon by human
intervention. Floorplanning places critical elements close to each other on the Xilinx
die, reducing net delays. The PACE and Floorplanner tools in ISE may be used for this.
A more advanced tool, PlanAhead, is also available separately from Xilinx to aid in
this task.
7.
Use a faster part. This is often the first solution seized upon, but is also expensive. If
you are using an old Xilinx part, porting your design to a newer, faster Xilinx part may
often save money because the new parts may be cheaper on account of Moore's Law.
However, moving to a faster part in the same family incurs significant extra costs, and
often isn't necessary if the previous steps are followed.
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Timing Analysis Tutorial
Sometimes the hardware created by System Generator may not meet the requested timing
requirements. This is typically due to a setup time violation in the design. A setup time
violation means that a particular signal cannot get from the output of one synchronous
element to the input of another synchronous element within the requested clock period
and subject to the second synchronous element's setup time requirement.
Let us use an example to show how we would use the timing analyzer to improve circuit
performance. Our example will be a parity calculator that will find the parity of a byte by
using an 8-input XOR. The design can be found at:
<sysgen_tree>/examples/timing_analysis/parity_test.mdl
The design has eight one-bit gateway inputs that are registered by one-bit registers. These
are processed by seven 2-input XOR blocks. These have a latency of zero and thus are
purely combinational. The final register, parity_reg, registers the final result (the parity)
which is connected to an output gateway. The design appears to have three levels of logic,
because each path fanning in to parity_reg goes through three XOR blocks.
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Generate the Example Design
We'll generate the design using the Timing Analysis target and a requested period of 1.4ns
(714MHz). This is admittedly a very high clock frequency, but we wish some paths to fail
for demonstration purposes. We set these parameters in the System Generator token:
Examine the Slow Paths
After clicking on Generate, after a time, the timing analyzer window will appear as shown
below:
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There are two failing paths, normally highlighted in red/pink. (The top path is gray
because it is selected.) The negative slack values are shown in boldface. The worst of the
two fails by 96ps.
Note that there are two levels of logic in the path shown. How can this be? The System
Generator diagram shows three levels of logic in all paths. The reason is that the
implemented design does not correlate exactly to the System Generator diagram. In this
case, the synthesizer has compressed some of the 2-bit XOR blocks into 4-input LUTs and
created the 8-input XOR using only two levels of logic as shown in this Synplify Pro
schematic:
LUT4_6996
LUT2_L_6
registerh_q_net[0:0]
registerg_q_net[0:0]
registerf_q_net[0:0]
registere_q_net[0:0]
xor_3a_y_net[0:0]
y_5[0]
y[0]
LUT4_6996
registerd_q_net[0:0]
registerc_q_net[0:0]
registerb_q_net[0:0]
registera_q_net[0:0]
y_4[0]
Note how the net and block names have all been munged, requiring the magic unmunging capabilities of the timing analyzer.
Also note the details of the selected path. The logic delays cannot be reduced. One of the
net delays is 813ps. This could possibly be reduced by means of floorplanning, multipass
PAR, or simply by increasing the PAR effort level.
Rescue the Design
Instead, let us attempt a more robust solution to fix the path by changing the source design.
There are no feedback paths in this design, so let us assume we can add a cycle of latency
and pipeline the design. There are two levels of logic in the failing paths. Any design can
theoretically be re-implemented with only a single level of logic. We will do this now.
To add a pipeline stage, we will merely add latency to selected XOR blocks. By clicking on
an XOR block, you may change its latency from zero to one like so:
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This will add a register to the end of the XOR gate. We will change the latency on blocks
xor_2a and xor_2b. We know from examining the Synplify Pro schematic that the
outputs of these blocks form the output of the first level of logic in the synthesized design.
The modified System Generator looks very similar with the exception of the z-1 on the
labels of the two modified XOR blocks, indicating their new latency.
We generate this design as before and examine the slow paths:
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Excellent! No more failing paths! The design has been rescued, all in record time and
without using a more expensive part. Surely raises and promotions shall follow you for all
your days.
Note that all paths now have but a single level of logic. What exactly has happened here?
Let us examine the Synplify Pro schematic to see how the modified circuit was
synthesized:
xor_2b_f0fd230c1d
LUT4_L_6996
xor_3a_7e73f4292b
LUT2_L_6
1.18,0.45
0.35,-0.06
0.98,0.45
0.98,0.45
1.18,0.45
1.18,0.45
0.98,0.45
0.98,0.45
parity_reg_3123b0b42f
1.18,-0.06
FD
D
Q
C
0.35,-0.06
0.98,-0.06
0.98,-0.06
1.18,-0.06
latency_pipe_5_26_0_
fully_2_1_bit[0]
y[0]
xor_3a
1.43,-0.06
1.43,-0.06
FD
D
Q
C
op_mem_19_20_0_
parity_reg
xor_2b
xor_2a_8d6908ffef
LUT4_L_6996
1.18,0.45
0.35,-0.06
0.98,0.45
0.98,0.45
0.98,0.45
1.18,0.45
1.18,0.45
0.98,0.45
FD
D
Q
C
0.35,-0.06
latency_pipe_5_26_0_
fully_2_1_bit[0]
xor_2a
See that there is an extra set of registers (highlighted in red) in between the two levels of
logic. The circuit functions the same as before but with an additional cycle of latency.
Use Retiming to Rescue the Design
If a cycle of latency had to be eliminated to match the latency of the original design, it
might be possible to remove the final output register or the input registers. This would
increase the constraints upon the paths outside the Xilinx chip (i.e., the copper paths on the
PCB), but it may be feasible depending upon board-level path delays. This would be an
example of retiming, because the latency is the same but the registers have been moved into
the logic "cloud".
Creating Compilation Targets
The HDL and netlist files that System Generator produces when it compiles a design into
hardware must be run through additional tools in order to produce a configuration
bitstream file that is suitable for your FPGA. A typical flow that allows you to generate an
FPGA configuration file is ProjectNavigator. There are other ways in which a bitstream can
be generated for your model. For example, it is possible to configure System Generator to
automatically run the tools necessary to produce a configuration file when it compiles a
design. This is advantageous since the complete bitstream generation process is
accomplished inside the tool. Moreover, you can have System Generator run different tools
(e.g., ChipScope Pro Analyzer and iMPACT) once the configuration file is generated for a
model.
The way in which System Generator compiles a model into hardware depends on the
compilation target that is chosen for the design. The HDL Netlist compilation target is
most common, and generates an HDL netlist of your design plus any cores that go along
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with it. New compilation targets can be created that extend the HDL Netlist target so that
additional tools can be applied to the resulting HDL netlist files.
This topic explains how you can create new compilation targets that extend the HDL
Netlist target in order to produce and configure FPGA hardware. More specifically, it
describes how to configure System Generator to produce a bitstream for a model, and how
to invoke various tools once the bitstream is created.
Defining New Compilation Targets
You can create new compilation targets to run tools that process the output files associated
with HDL Netlist compilation. A compilation target is defined by a minimum of two
MATLAB functions. The first function, xltarget.m, tells System Generator to support
the target (i.e., make it selectable from the System Generator block dialog box), and
specifies the MATLAB function where more information about the target can be found.
This function is called a "target info" function. A target info function defines information
about the target, and can take any name, provided it is specified correctly in the target's
xltarget.m function. In some cases, a target info function defines a post-generation
function. A post-generation function is responsible for invoking tools or scripts after
normal HDL netlist compilation is complete. These functions are discussed in more detail
in the topics that follow.
The xltarget Function
An xltarget function specifies one or more compilation targets that should be supported by
System Generator. It also provides entry points through which System Generator can find
out more information about these targets.
Note: System Generator determines which compilation targets to support by searching the
plugins/compilation (and its subdirectories) of your System Generator software install tree for
xltarget.m files.
Although an xltarget function can specify multiple targets, it is not uncommon for each
compilation target to have its own xltarget function. The directories these functions are
saved in distinguish the targets. This means that each xltarget.m file must be saved in
its own subdirectory under the plugins/compilation directory.
An xltarget function returns a cell array of target information. Different elements in this
cell array define different compilation targets. The elements in this cell array are MATLAB
structs that define two parameters:
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1.
The name of the compilation target as it should appear in the Compilation field of the
System Generator parameters dialog box;
2.
The name of the MATLAB function it should invoke to find out more information (e.g.,
System Generator dialog box parameters, which post-generation function to use, if
any) about the target.
The following code shows how to define three compilation targets named Standalone
Bitstream, iMPACT, and ChipScope Pro Analyzer:
function s = xltarget
s = {};
target_1.('name') = 'Standalone Bitstream';
target_1.('target_info') = 'xltools_target';
target_2.('name') = 'iMPACT';
target_2.('target_info') = 'xltools_target';
target_3.('name') = 'ChipScope Pro Analyzer';
target_3.('target_info') = 'xltools_target';
s = {target_1, target_2, target_3};
The name field in the code shown above specifies the name of the compilation target, as it
should appear in the Compilation field of the System Generator dialog box:
target_1.('name') = 'Standalone Bitstream';
The target_info field tells System Generator the target info function it should call to find
out more information about the target. This function can have any name provided it is
saved in the same directory as the corresponding xltarget.m file, or it is saved somewhere
in the MATLAB path.
target_1.('target_info') = 'xltools_target';
Note: An example xltarget function is included in the examples/comp_targets directory of your
System Generator install tree. You can modify this function to define your own bitstream-related
compilation targets.
Target Info Functions
A target info function (specified by the target_info field in the code above) is responsible
for two things:
•
It defines the available and default settings for the target in the System Generator
block dialog box;
•
It specifies the functions System Generator should call before and after the standard
code generation process.
Note: An example target info function, xltools_target.m, is included in the
examples/comp_targets directory of your System Generator install tree.
One such function that is particularly useful to compilation targets is the post-generation
function. A post-generation function is run after standard code generation. The code below
shows how a post-generation function is specified in a target info function:
settings.('postgeneration_fcn') = 'xltools_postgeneration';
Post-generation Functions
One way to extend System Generator compilation is by defining a new variety of
compilation that specifies a post-generation function. A post-generation function is a
MATLAB function that tells System Generator how to process the HDL and netlist files
once they are generated. This function is run after System Generator finishes the normal
code generation steps involved with HDL Netlist compilation (i.e., producing an HDL
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description of the design, running CORE Generator, etc). For example, a hardware cosimulation target defines a post-generation function that in turn runs the tools necessary to
produce hardware that can be used in the Simulink simulation loop.
Note: Two post-generation functions xlBitstreamPostGeneration.m and
xltools_postgeneration.m, are included in the examples/comp_targets directory of your
System Generator install tree.
xlBitstreamPostGeneration.m
This example post-generation function compiles your model into a configuration bitstream
that is appropriate for the settings (e.g., FPGA part, clock frequency, clock pin location)
given in the System Generator dialog box of your design.
It then uses an XFLOW-based flow to invoke the Xilinx tools necessary to produce an
FPGA configuration bitstream.
It is possible to configure the tools and configurations for each tool invoked by XFLOW.
For more information on how to do this, refer to the topic in this example entitled Using
XFLOW
xltools_postgeneration.m
Sometimes you may want to run tools that configure and run the FPGA after a
configuration bitstream has been generated (e.g., iMPACT, ChipScope Pro Analyzer). The
xltools_postgeneration function first calls the xlBitstreamGeneration function to generate
the bitstream. It then invokes the appropriate tool (or tools) depending on the compilation
target that is selected.
For example, you may want a compilation target that invokes iMPACT after the bitstream
is generated. This can be done as follows (assuming iMPACT is in your system path):
if (strcmp(params.compilation, 'iMPACT'))
dos('impact');
end;
The first line checks the name of the compilation target. The second line sets up a DOS
command that invokes iMPACT. ChipScope Pro Analyzer can be invoked similarly to the
code above:
if (strcmp(params.compilation, 'ChipScope Pro Analyzer'))
xlCallChipScopeAnalyzer;
end;
Note: xlCallChipScopeAnalyzer is a MATLAB function provided by System Generator to invoke
ChipScope.
Configuring and Installing the Compilation Target
Listed below are the steps necessary to configure and install new bitstream compilation
targets.
1.
Copy the xltarget.m, xltools_postgeneration.m, and xltools_target.m
files from examples/comp_targets into a temporary directory.
2.
Change the permissions of the above files so they can be modified.
3.
Add the desired compilation targets (e.g., iMPACT, ChipScope Analyzer Pro) to the
xltarget.m file.
4.
Add the desired tool invocations to the xltools_postgeneration.m file.
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5.
Create a new directory (e.g., Bitstream) under the plugins/compilation directory
of your System Generator software install tree. Copy the xltarget.m,
xltools_postgeneration.m, and xltools_target.m files into this directory.
Note: The System Generator Compilation submenus mirror the directory structure under the
plugins/compilation directory. When you create a new directory, or directory hierarchy, for the
compilation target files, the names of the directories define the taxonomy of the compilation target
submenus.
6.
Copy the xlBitstreamPostGeneration.m, xlToolsMakebit.pl,
balanced_xltools.opt and bitgen_xltools.opt files from the
examples/comp_targets directory into a directory that is in your MATLAB path.
These files must be in a common directory.
7.
In the MATLAB command window, type the following:
>> rehash toolboxcache
>> xlrehash_xltarget_cache
8.
You can now access the newly installed compilation target from the System Generator
graphical interface.
Using XFLOW
The post-generation scripting included with this example uses XFLOW to produce a
configuration file for your FPGA. XFLOW allows you to automate the process of design
synthesis, implementation, and simulation using a command line interface. XFLOW uses
command files to tell it which tools to run, and how they should be run.
This example contains two XFLOW options files, balanced_xltools.opt and
bitgen_xltools.opt. These files are associated with the implementation and
configuration flows of XFLOW, respectively. The balanced_xltools.opt options files
runs the Xilinx NGDBUILD, MAP, and PAR tools. The settings for each tool are specified in
the options files . The bitgen_xltools.opt file runs BITGEN to produce a
configuration file for your FPGA. You may modify these files as desired (e.g., to run the
timing analyzer after PAR).
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Index
A
importing a Verilog module
creating new compilation targets
307
importing a VHDL module 300
importing a Xilinx Core Generator module 286
simulating several black boxes
simultaneously 311
HDL Co-Sim
configuring the HDL simulator
Addressable Shift Register block 15
Algorithm Exploration 17
ASR block 15
Asynchronous Clocking 25
Auto-Generated Clock Enable Logic
resetting in System Generator 95
Automatic Code Generation 38
B
Bit-Accurate 20
Bitstream Compilation 321
Bit-True Modeling 23
Black Box
Configuration M-Function
adding new ports 273
black box API 279
black box clocking 276
combinational paths 277
configuring port sample rates
275
configuring port types 274
defining block ports 273
dynamic output ports 276
error checking 278
language selection 273
obtaining a port object 274
specifying the top-level entity
273
specifying Verilog parameters
277
specifying VHDL Generics 277
SysgenBlockDescriptor Member Variables 279
SysgenBlockDescriptor methods 280
SysgenPortDescriptor Member
Variables 282
SysgenPortDescriptor methods
282
Examples 286
advanced black box example using ModelSim 313
dynamic black boxes 309
importing a Core Generator
module 287
importing a Core Generator
module that needs a VHDL
wrapper 293
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co-simulating multiple black
boxes 285
Black Box Configuration
M-function 272
Black Box Configuration Wizard 270
Block Masks 35
Blockset
Xilinx 21
C
ChipScope Pro Analyzer 126
Clock Domain Partitioning 115
Clock Enable
Fanout Reduction 88
Clock Frequency
selecting for Hardware Co-Sim 180
Clock Generator(DCM) Option
locked pin 26
reset pin 26
tutorial 27
Clocking
and timing 23
asynchronous 25
synchronous 25
Clocking Options
Clock Enable 26
Clock Generator(DCM) 26
Expose Clock Ports 27
Code Generation
automatic 38
Color Shading
blocks by signal rate 23
Compilation Type
using XFLOW 346
Compilation Types
Bitstream Compilation 321
configuring and installing the Compilation Target 345
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EDK Export Tool 325
Hardware Co-Simulation Compilation 329
HDL Netlist Compilation 320
NGC Netlist Compilation 320
Compiling for
bitstream generation 321
EDK Export 325
Hardware Co-Simulation 329
NGC Netlist generation 320
Compiling for HDL Netlist generation
320
Compiling MATLAB
complex multiplier with latency 53
disp function 69
finite state machines 60
FIR example 64
into an FPGA 49
optional input ports 58
parameterizable accumulator 61
passing parameters into the MCode
block 55
RPN calculator 67
shift operation 54
simple arithmetic operation 51
simple selector 50
Compiling Shared Memories
for HW Co-Sim 190
Configurable Subsystems and System
Generator 81
Configuring and Installing the Compilation Target 345
Constraints File
System Generator 44
Controls
hierarchical 42
Creating Compilation Targets 342
Crossing Clock Domains 116
Custom Bus Interfaces
for exported pcore 326
Cycle-Accurate 20
Cycle-True Clock Islands 114
Cycle-True Modeling 23
D
Debugging
347
R
using ChipScope Pro 126
Defining New Compilation Targets 343
Target Info functions
xltools_target 344
the xltarget Function 343
Discrete Time Systems 23
Distinct Clocks
generating multiple cycle-true islands 114
DSP48
design styles for 98
design techniques 102
mapping from the DSP48 block 100
mapping standard components to
99
mapping to from logic synthesis
tools 99
physical planning for 104
DSP48 Macro block 101
E
EDK
generating software drivers 141
support from System Generator 145
writing software drivers 142
EDK Export Tool 325
exporting a pcore 148
EDK Import Wizard 145
EDK Processor
exposing processor ports 147
importing 145
Ethernet-based HW Co-Sim 242
Export pcore
enable Custom Bus Interfaces 326
Exporting
a pcore 148
a System Generator model as a pcore
140
Expose Clock Ports Option
tutorial 32
G
Generating
an FPGA bitstream 92
EDK software drivers 141
Generating an FPGA Bitstream
Generating an FPGA Bitstream 92
H
Hardware
oversampling 25
Hardware Co-Sim 175
blocks 177
choosing a compilation target 176
compiling shared memories 190
co-simulating lockable shared memories 193
co-simulating shared FIFOs 196
co-simulating shared registers 195
co-simulating unprotected shared
memories 192
invoking the code generator 176
JTAG hardware requirements 255
Network-Based Ethernet 188
Point-to-Point Ethernet 184
processor integration 141
restrictions on shared memories 199
selecting the target clock frequency
180
shared memory support 189
using for frame-based acceleration
Fanout Reduction
for Clock Enable 88
FDATool
using in digital filter applications
106
FPGA
a brief introduction 12
generating a bitstream 92
notes for higher performance 87
designing and simulating MicroBlaze Processor Systems
160
using EDK 169
using PicoBlase in System Generator 150
HDL Co-Sim
configuring the HDL simulator 283
co-simulating multiple black boxes
285
HDL Netlist Compilation 320
HDL Testbench 49
Hierarchical Controls 42
Histogram Charts
from Timing Analyzer 334, 336
I
Implementing
a complete design 17
part of a design 17
Importing
a System Generator design 71
an EDK processor 145
an EDK project 140
Importing a System Generator Design 71
integration design rules 71
integration flow with Project Navigator 72
step-by-step example 73
Installation
Installing a Spartan-3A DSP 1800A
Starter Platform for Hardware CoSim 242
Installing am ML402 Board for JTAG
Hardware Co-Sim 254
Introduction
to FPGAs 12
201
using for real-time signal processing
214
Xilinx tool flow settings 199
Hardware Co-Simulation Compilation
329
F
348
Frame-Based Acceleration
using Hardware Co-Sim 201
FSL-based pcore 138
Full Precision signal type 22
Hardware Debugging
using ChipScope Pro 126
Hardware Generation 140
Hardware Generation Mode
EDK pcore 140
HDL netlist 140
Hardware/Software Co-Design 138
Examples
creating MicroBlaze Peripherals
in System Generator 155
www.xilinx.com
J
JTAG Hardware Co-Sim
board support package files 261
Detecting New Board Packages 267
installing board-support packages
266
manually specifying board-specific
ports 264
obtaining platform information 262
providing your own top-level 265
supporting new platforms 255
JTAG-based HW Co-Sim 254
System Generator for DSP
Release 10.1.1 April, 2008
R
produced by System Generator 42
Oversampling 25
L
Locked pin
Clock Generator(DCM) Option 26
M
MATLAB
compiling into an FPGA 49
complex multiplier with latency 53
disp function 69
finite state machines 60
FIR example 64
optional input ports 58
parameterizable accumulator 61
passing parameters into the MCode
block 55
RPN calculator 67
simple arithmetic operation 51
simple selector 50
simple shift operation 54
Memory Map Creation
for processor integration 139
M-Function
black box configuration 272
MicroBlaze
in System Generator tutorial 155
System Design and Simulation 160
ML402 Board
Installation for JTAG HW Co-Sim
254
Modeling
bit-true and cycle-true 23
Multiple Clock Applications 114
Multirate Designs
color shading by signal rate 23
Multirate Models 24
N
Netlisting
multiple clock designs 117
Network-Based Ethernet Hardware CoSim 188
NGC Netlist Compilation 320
Notes
for higher performance FPGA design
87
O
OutputFiles
System Generator for DSP
Release 10.1.1 April, 2008
P
Parameter Passing 36
Pcore
export as under development 325
pcore
exporting 148
exporting a System Generator model
as a peripheral 140
PicoBlaze
designing within System Generator
148
in System Generator tutorial 150
overview 148
PLB-based pcore 138
Point-to-Point Ethernet HW Co-Sim 184
Processor Integration
Hardware Co-Sim 141
hardware generation 140
memory map creation 139
using custom logic 138
Project Navigator
integration flow with System Generator 72
R
Rate-Changing Blocks 24
Real-Time Signal Processing
using Hardware Co-Sim 214
Reducing
Clock Enable Fannout 88
Reference Blockset
Xilinx 21
Reset pin
Clock Generator(DCM) Option 26
Resource Estimation 38
S
gateway blocks 22
user-specified precision 22
Simulink System Period 41
Spartan-3A DSP 1800A Starter Platform
Installation for Ethernet HW Co-Sim
242
Synchronization Mechanisms
indeterminate data 35
valid ports 35
Synchronous Clocking 25
Clock Enable option 26
Clock Generator(DCM) option 26
Expose Clock Ports option 27
System Generator
adding a block to a Configurable
Subsystem 84
and Configurable Subsystems 81
blocksets 20
defining a Configurable Subsystem
81
deleting a block from a Configurable
Subsystem 84
generating hardware from Configurable Subsystems 85
output files 42
processing a design with physical
design tools 88
resetting auto-generated Clock Enable logic 95
system-level modeling 19
using a Configurable Subsystem 83
System Generator block
compiling and simulating 39
System Generator Constraints
constraints file 44
example 45
IOB timing and placement 44
multicycle path 44
system clock period 44
System Generator Design Flows
algorithm exploration 17
implementing a complete design 17
implementing part of a larger design
17
SBD Builder
saving plugin files 260
specifying board-specific I/O ports
258
Shared Memory Support
for HW Co-Sim 189
Signal Types 22
displaying data types 22
full precision 22
www.xilinx.com
System-Level Modeling 19
T
Tapped Delay Lines 15
TDM data streams 15
Testbench
HDL 49
Time-Division Multiplexed 15
349
R
export pcore as 325
Using XFLOW 346
Timing Analysis
clock skew and jitter 331
compilation type
Compiling for
timing analysis
329
concepts review 330
cross-probing 333
displaying low-level names 333
histogram charts 334, 336
improving failing paths 336
observing slow paths 332
path analysis example 331
period and slack 330
statistics 335
trace report 335
tutorial 338
Timing Analyzer
invoking on previously-generated
data 330
Timing and Clocking 23
Trace Report
timing analysis 335
Tutorials
Black Box
Dynamic Black Boxes 309
Importing a Core Generator
Module 287
Importing a Core Generator
Module that Needs a VHDL
Wrapper 293
Importing a Verilog Module
308
Importing a VHDL Module 300
Simulating Several Black Boxes
Simultaneously 311
Clocking
Using the Clock Generator(DCM) Option 27
Using the Expose Clock Ports
Option 32
Hardware/Software Co-Design
Creating a New XPS Project 169
Creating MicroBlaze Peripherals in System Generator 155
Designing and Simulating MicroBlaze Processor Systems
V
Variable Clock Frequency
selecting for Hardware Co-Sim 180
W
Wizards
Base System Builder 169
Black Box Configuration 270, 300
EDK Import 145
XPS Import 162
X
Xilinx
Blockset 21
Reference Blockset 21
Xilinx Tool Flow Settings
for HW Co-Sim 199
xlCallChipScopeAnalyzer 345
xlmax 50
xlSimpleArith 51
xltarget
defining new Compilation Targets
343
xlTimingAnalysis 330
xltools_postgeneration 344, 345
xltools_target 344
XPS Import Wizard 162
160
Using PicoBlaze in System Generator 150
Timing Analysis 338
U
Underdevelopment
350
www.xilinx.com
System Generator for DSP
Release 10.1.1 April, 2008
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