Intel® Quartus® Prime Standard Edition User Guide: Design Recommendations

Download PDF
ID 683323
Date 9/24/2018
Public
Document Table of Contents
Document Table of Contents x
1. Recommended Design Practices 2. Recommended HDL Coding Styles 3. Managing Metastability with the Intel® Quartus® Prime Software A. Intel® Quartus® Prime Standard Edition User Guides
1. Recommended Design Practices x
1.1. Following Synchronous FPGA Design Practices 1.2. HDL Design Guidelines 1.3. Checking Design Violations 1.4. Use Clock and Register-Control Architectural Features 1.5. Implementing Embedded RAM 1.6. Recommended Design Practices Revision History
1.1. Following Synchronous FPGA Design Practices x
1.1.1. Implementing Synchronous Designs 1.1.2. Asynchronous Design Hazards
1.2. HDL Design Guidelines x
1.2.1. Optimizing Combinational Logic 1.2.2. Optimizing Clocking Schemes 1.2.3. Optimizing Physical Implementation and Timing Closure 1.2.4. Optimizing Power Consumption 1.2.5. Managing Design Metastability
1.2.1. Optimizing Combinational Logic x
1.2.1.1. Avoid Combinational Loops 1.2.1.2. Avoid Unintended Latch Inference 1.2.1.3. Avoid Delay Chains in Clock Paths 1.2.1.4. Use Synchronous Pulse Generators
1.2.2. Optimizing Clocking Schemes x
1.2.2.1. Register Combinational Logic Outputs 1.2.2.2. Avoid Asynchronous Clock Division 1.2.2.3. Avoid Ripple Counters 1.2.2.4. Use Multiplexed Clocks 1.2.2.5. Use Gated Clocks 1.2.2.6. Use Synchronous Clock Enables
1.2.2.5. Use Gated Clocks x
1.2.2.5.1. Recommended Clock-Gating Methods
1.2.3. Optimizing Physical Implementation and Timing Closure x
1.2.3.1. Planning Physical Implementation 1.2.3.2. Planning FPGA Resources 1.2.3.3. Optimizing for Timing Closure 1.2.3.4. Optimizing Critical Timing Paths
1.3. Checking Design Violations x
1.3.1. Validating Against Design Rules 1.3.2. Creating Custom Design Rules
1.3.2. Creating Custom Design Rules x
1.3.2.1. Custom Design Rule Examples
1.4. Use Clock and Register-Control Architectural Features x
1.4.1. Use Global Reset Resources 1.4.2. Use Global Clock Network Resources 1.4.3. Use Clock Region Assignments to Optimize Clock Constraints 1.4.4. Avoid Asynchronous Register Control Signals
1.4.1. Use Global Reset Resources x
1.4.1.1. Use Synchronous Resets 1.4.1.2. Using Asynchronous Resets 1.4.1.3. Use Synchronized Asynchronous Reset
1.4.3. Use Clock Region Assignments to Optimize Clock Constraints x
1.4.3.1. Clock Region Assignments in Intel® Arria® 10 and Older Device Families
2. Recommended HDL Coding Styles x
2.1. Using Provided HDL Templates 2.2. Instantiating IP Cores in HDL 2.3. Inferring Multipliers and DSP Functions 2.4. Inferring Memory Functions from HDL Code 2.5. Register and Latch Coding Guidelines 2.6. General Coding Guidelines 2.7. Designing with Low-Level Primitives 2.8. Recommended HDL Coding Styles Revision History
2.1. Using Provided HDL Templates x
2.1.1. Inserting HDL Code from a Provided Template
2.3. Inferring Multipliers and DSP Functions x
2.3.1. Inferring Multipliers Verilog HDL Unsigned Multiplier Verilog HDL Signed Multiplier with Input and Output Registers (Pipelining = 2) VHDL Unsigned Multiplier with Input and Output Registers (Pipelining = 2) VHDL Signed Multiplier 2.3.2. Inferring Multiply-Accumulator and Multiply-Adder Functions
2.4. Inferring Memory Functions from HDL Code x
2.4.1. Inferring RAM functions from HDL Code 2.4.2. Inferring ROM Functions from HDL Code 2.4.3. Inferring Shift Registers in HDL Code
2.4.1. Inferring RAM functions from HDL Code x
2.4.1.1. Use Synchronous Memory Blocks 2.4.1.2. Avoid Unsupported Reset and Control Conditions 2.4.1.3. Check Read-During-Write Behavior 2.4.1.4. Controlling RAM Inference and Implementation 2.4.1.5. Single-Clock Synchronous RAM with Old Data Read-During-Write Behavior 2.4.1.6. Single-Clock Synchronous RAM with New Data Read-During-Write Behavior 2.4.1.7. Simple Dual-Port, Dual-Clock Synchronous RAM 2.4.1.8. True Dual-Port Synchronous RAM 2.4.1.9. Mixed-Width Dual-Port RAM 2.4.1.10. RAM with Byte-Enable Signals 2.4.1.11. Specifying Initial Memory Contents at Power-Up
2.4.3. Inferring Shift Registers in HDL Code x
2.4.3.1. Simple Shift Register 2.4.3.2. Shift Register with Evenly Spaced Taps
2.5. Register and Latch Coding Guidelines x
2.5.1. Register Power-Up Values 2.5.2. Secondary Register Control Signals Such as Clear and Clock Enable 2.5.3. Latches
2.5.1. Register Power-Up Values x
2.5.1.1. Specifying a Power-Up Value
2.5.3. Latches x
2.5.3.1. Avoid Unintentional Latch Generation 2.5.3.2. Inferring Latches Correctly
2.6. General Coding Guidelines x
2.6.1. Tri-State Signals 2.6.2. Clock Multiplexing 2.6.3. Adder Trees 2.6.4. State Machine HDL Guidelines 2.6.5. Multiplexer HDL Guidelines 2.6.6. Cyclic Redundancy Check Functions 2.6.7. Comparator HDL Guidelines 2.6.8. Counter HDL Guidelines
2.6.3. Adder Trees x
2.6.3.1. Architectures with 4-Input LUTs in Logic Elements 2.6.3.2. Architectures with 6-Input LUTs in Adaptive Logic Modules
2.6.4. State Machine HDL Guidelines x
2.6.4.1. Verilog HDL State Machines 2.6.4.2. VHDL State Machines
2.6.4.1. Verilog HDL State Machines x
2.6.4.1.1. Verilog-2001 State Machine Coding Example 2.6.4.1.2. SystemVerilog State Machine Coding Example
2.6.4.2. VHDL State Machines x
2.6.4.2.1. VHDL State Machine Coding Example
2.6.5. Multiplexer HDL Guidelines x
2.6.5.1. Intel® Quartus® Prime Software Option for Multiplexer Restructuring 2.6.5.2. Multiplexer Types 2.6.5.3. Implicit Defaults in IF Statements 2.6.5.4. default or OTHERS CASE Assignment
2.6.5.2. Multiplexer Types x
2.6.5.2.1. Binary Multiplexers 2.6.5.2.2. Selector Multiplexers 2.6.5.2.3. Priority Multiplexers
2.6.6. Cyclic Redundancy Check Functions x
2.6.6.1. If Performance is Important, Optimize for Speed 2.6.6.2. Use Separate CRC Blocks Instead of Cascaded Stages 2.6.6.3. Use Separate CRC Blocks Instead of Allowing Blocks to Merge 2.6.6.4. Take Advantage of Latency if Available 2.6.6.5. Save Power by Disabling CRC Blocks When Not in Use 2.6.6.6. Initialize the Device with the Synchronous Load (sload) Signal
3. Managing Metastability with the Intel® Quartus® Prime Software x
3.1. Metastability Analysis in the Intel® Quartus® Prime Software 3.2. Metastability and MTBF Reporting 3.3. MTBF Optimization 3.4. Reducing Metastability Effects 3.5. Scripting Support 3.6. Managing Metastability 3.7. Managing Metastability with the Intel® Quartus® Prime Software Revision History
3.1. Metastability Analysis in the Intel® Quartus® Prime Software x
3.1.1. Synchronization Register Chains 3.1.2. Identify Synchronizers for Metastability Analysis 3.1.3. How Timing Constraints Affect Synchronizer Identification and Metastability Analysis
3.2. Metastability and MTBF Reporting x
3.2.1. Metastability Reports 3.2.2. Synchronizer Data Toggle Rate in MTBF Calculation
3.2.1. Metastability Reports x
3.2.1.1. MTBF Summary Report 3.2.1.2. Synchronizer Summary Report 3.2.1.3. Synchronizer Chain Statistics Report in the Timing Analyzer
3.2.1.1. MTBF Summary Report x
3.2.1.1.1. Typical and Worst-Case MTBF of Design 3.2.1.1.2. Synchronizer Chains 3.2.1.1.3. Increasing Available Settling Time
3.3. MTBF Optimization x
3.3.1. Synchronization Register Chain Length
3.4. Reducing Metastability Effects x
3.4.1. Apply Complete System-Centric Timing Constraints for the Timing Analyzer 3.4.2. Force the Identification of Synchronization Registers 3.4.3. Set the Synchronizer Data Toggle Rate 3.4.4. Optimize Metastability During Fitting 3.4.5. Increase the Length of Synchronizers to Protect and Optimize 3.4.6. Set Fitter Effort to Standard Fit instead of Auto Fit 3.4.7. Increase the Number of Stages Used in Synchronizers 3.4.8. Select a Faster Speed Grade Device
3.5. Scripting Support x
3.5.1. Identifying Synchronizers for Metastability Analysis 3.5.2. Synchronizer Data Toggle Rate in MTBF Calculation 3.5.3. report_metastability and Tcl Command 3.5.4. MTBF Optimization 3.5.5. Synchronization Register Chain Length
1. Recommended Design Practices
2. Recommended HDL Coding Styles
3. Managing Metastability with the Intel® Quartus® Prime Software
A. Intel® Quartus® Prime Standard Edition User Guides

2.3.1. Inferring Multipliers

To infer multiplier functions, synthesis tools detect multiplier logic and implement this in Intel FPGA IP cores, or map the logic directly to device atoms.

For devices with DSP blocks, Intel® Quartus® Prime synthesis can implement the function in a DSP block instead of logic, depending on device utilization. The Intel® Quartus® Prime fitter can also place input and output registers in DSP blocks (that is, perform register packing) to improve performance and area utilization.

The following Verilog HDL and VHDL code examples show that synthesis tools can infer signed and unsigned multipliers as IP cores or DSP block atoms. Each example fits into one DSP block element. In addition, when register packing occurs, no extra logic cells for registers are required.

Verilog HDL Unsigned Multiplier

module unsigned_mult (out, a, b);
	output [15:0] out;
	input [7:0] a;
	input [7:0] b;
	assign out = a * b;
endmodule
Note: The signed declaration in Verilog HDL is a feature of the Verilog 2001 Standard.

Verilog HDL Signed Multiplier with Input and Output Registers (Pipelining = 2) 

module signed_mult (out, clk, a, b);
   output [15:0] out;
   input clk;
   input signed [7:0] a;
   input signed [7:0] b;

   reg signed [7:0] a_reg;
   reg signed [7:0] b_reg;
   reg signed [15:0] out;
   wire signed [15:0] mult_out;

   assign mult_out = a_reg * b_reg;

   always @ (posedge clk)
   begin
      a_reg <= a;
      b_reg <= b;
      out <= mult_out;
   end
endmodule

VHDL Unsigned Multiplier with Input and Output Registers (Pipelining = 2) 

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;

ENTITY unsigned_mult IS
   PORT (
      a: IN UNSIGNED (7 DOWNTO 0);
      b: IN UNSIGNED (7 DOWNTO 0);
      clk: IN STD_LOGIC;
      aclr: IN STD_LOGIC;
      result: OUT UNSIGNED (15 DOWNTO 0)
   );
END unsigned_mult;

ARCHITECTURE rtl OF unsigned_mult IS
   SIGNAL a_reg, b_reg: UNSIGNED (7 DOWNTO 0);
BEGIN
   PROCESS (clk, aclr)
   BEGIN
      IF (aclr ='1') THEN
         a_reg <= (OTHERS => '0');
         b_reg <= (OTHERS => '0');
         result <= (OTHERS => '0');
      ELSIF (rising_edge(clk)) THEN
         a_reg <= a;
         b_reg <= b;
         result <= a_reg * b_reg;
      END IF;
   END PROCESS;
END rtl;

VHDL Signed Multiplier

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;

ENTITY signed_mult IS
   PORT (
      a: IN SIGNED (7 DOWNTO 0);
      b: IN SIGNED (7 DOWNTO 0);
      result: OUT SIGNED (15 DOWNTO 0)
   );
END signed_mult;

ARCHITECTURE rtl OF signed_mult IS
BEGIN
   result <= a * b;
END rtl;
Level Two Title