Xilinx UG144 Pause Control Frames

1-Gigabit Ethernet MAC v8.5 User Guide www.xilinx.com 55

UG144 April 24, 2009

Overview of Flow Control

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-- DISCONTINUED PRODUCT --

Pause Control Frames

Control frames are a unique type of Ethernet frame, defined in clause 31 of the IEEE 802.3-

2005 standard. Control frames are differentiated from other frame types by a defined value

placed in the length/type field (MAC Control Type code). Figure6-2 illustrates the control

frame format.

A pause control frame is a unique type of control frame, identified by a defined value

placed in the MAC Control opcode field.

Note: MAC Control opcodes other than for pause (flow control) frames have recently been defined

for Ethernet Passive Optical Networks.

The MAC control parameter field of the pause control frame contains a 16-bit field

containing a binary value directly related to the pause duration. This defines the number of

pause_quantum (512 bit times of the particular implementation). For 1-Gigabit Ethernet,

a single pause_quantum corresponds to 512 ns.

Figure 6-2: MAC Control Frame Format

DESTINATION

ADDRESS

SOURCE

ADDRESS

LENGTH/TYPE

MAC CONTROL

OPCODE

MAC CONTROL

PARAMETERS

RESERVED

(transmitted as zeroes)

6 OCTETS

6 OCTETS

2 OCTETS

2 OCTETS FRAME

TRANSMITTED

TOP-TO-BOTTOM

44 OCTETS

FRAME CHECK

SEQUENCE

4 OCTETS

Contents

Main UG144 April 24, 2009 Revision History Page Table of Contents Schedule of Figures Schedule of Tables Preface: About This Guide Chapter 1: Introduction Chapter 2: Core Architecture Chapter 3: Generating the Core Chapter 4: Designing with the Core General Design Guidelines Using the MDIO interface Chapter 5: Using the Client Side Data Path Receiving Inbound Frames Chapter 8: Configuration and Status Using the Optional Management Interface Chapter 9: Constraining the Core Required Constraints Chapter 10: Clocking and Resetting Chapter 12: Implementing Your Design Appendix A: Using the Client-Side FIFO Appendix B: Core Verification, Compliance, and Interoperability Appendix C: Calculating DCM Phase-Shifting Appendix D: Core Latency Schedule of Figures Chapter 7: Using the Physical Side Interface Chapter 8: Configuration and Status Chapter 9: Constraining the Core Chapter 10: Clocking and Resetting Page Page Schedule of Tables Page Preface About This Guide Guide Contents Conventions Typographical Online Document List of Acronyms The following table describes acronyms used in this manual. Page Chapter 1 Introduction About the Core Recommended Design Experience Additional Core Resources Related Xilinx Ethernet Products and Services Specifications Technical Support Feedback GEMAC Core Document Core Architecture System Overview Core Components Transmit Engine Receive Engine Flow Control Address Filter Core Interfaces Client Side Interface Physical Side Interface (GMII) host_clk domain Figure 2-2: Component Pinout for MAC with Optional Management Interface GMAC Core with Optional Management Interface GMAC Core Without Management Interface and With Address Filter Core Interfaces GEMAC Core Without Management Interface and Without Address Filter Client Side Interface Transmitter Interface Receiver Interface Flow Control Interface Management Interface (Optional) MAC Unicast Address (Optional) Configuration Vector (Optional) Asynchronous Reset Physical Side Interface GMII MDIO Interface Chapter 3 Generating the Core Graphical User Interface Component Name Management Interface Address Filter Parameter Values in the XCO File Output Generation Page Chapter 4 Designing with the Core General Design Guidelines Design Steps Using the Example Design as a Starting Point Page Implementing the 1-Gigabit Ethernet MAC in Your Application Know the Degree of Difficulty Keep it Registered Recognize Timing Critical Signals Use Supported Design Flows Make Only Allowed Modifications Chapter 5 Using the Client Side Data Path Receiving Inbound Frames Normal Frame Reception rx_good_frame, rx_bad_frame timing Frame Reception with Errors Client-Supplied FCS Passing VLAN Tagged Frames Maximum Permitted Frame Length Length/Type Field Error Checks Enabled Disabled Address Filter Receiver Statistics Vector Page Page Transmitting Outbound Frames Normal Frame Transmission Paddin g Client-Supplied FCS Passing Client Underrun VLAN Tagged Frames Maximum Permitted Frame Length Inter-Frame Gap Adjustment Transmitter Statistics Vector Page Page Chapter 6 Using Flow Control Overview of Flow Control Flow Control Requirement Flow Control Basics Pause Control Frames Flow Control Operation of the GEMAC Transmitting a PAUSE Control Frame Core-initiated Pause Request Client Initiated Pause Request Receiving a Pause Control Frame Core Initiated Response to a Pause Request Pause Frame Reception Disabled Pause Frame Reception Enabled Client Initiated Response to a Pause Request Flow Control Implementation Example Method Page Page Chapter 7 Using the Physical Side Interface Implementing External GMII GMII Transmitter Logic Chapter 7: Using the Physical Side Interface Figure 7-1: External GMII Transmitter Logic GMII Receiver Logic Spartan-3, Spartan-3E, Spartan-3A and Virtex-4 Devices Page Page Chapter 7: Using the Physical Side Interface Implementing External RGMII Figure 7-4: External RGMII Transmitter Logic RGMII Transmitter Logic Spartan-3, Spartan-3E, Spartan-3A and Spartan-3A DSP Devices IOB LOGIC Page Page Page RGMII Receiver Logic Spartan-3, Spartan-3E, Spartan-3A and Spartan-3A DSP Devices Figure 7-7: External RGMII Receiver Logic IOB LOGIC 1-Gigabit Ethernet MAC Core DCM CLKIN CLK0 FB Page Figure 7-8: External RGMII Receiver Logic for Virtex-4 Devices 1-Gigabit Ethernet MAC Core DCM CLKIN CLK0 FB Page RGMII Inband Status Decoding Logic RGMII RECEIVER LOGIC Figure 7-10: RGMII Inband Status Decoding Logic 1-Gigabit Ethernet MAC Core Using the MDIO interface Connecting the MDIO to an Internally Integrated PHY Connecting the MDIO to an External PHY Chapter 8 Configuration and Status Using the Optional Management Interface Host Clock Frequency Configuration Registers Receiver Configuration Transmitter Configuration Flow Control Configuration MDIO Configuration Address Filter Configuration Writing and Reading to and from the Configuration Registers Page Accessing the Address Table MDIO Interface Introduction to MDIO Abbreviations Used Write Transaction Read Transaction Accessing MDIO With GEMAC --------------------------------------------------------------------= f f 1 Clock Divide[4:0]+()2 Page Access without the Management Interface Page Page Chapter 9 Constraining the Core Required Constraints Device, Package, and Speedgrade Selection I/O Location Constraints Placement Constraints PERIOD Constraints for Clock Nets gtx_clk gmii_rx_clk (for GMII Example Designs) rgmii_rxc (for RGMII Example Designs) host_clk Timespecs for Critical Logic within the Core Flow Control Configuration Timespecs for Reset Logic within the Core Constraints when Implementing an External GMII GMII IOB Constraints GMII Input Setup/Hold Timing Spartan-3, Spartan-3E, Spartan-3A and Virtex-4 Devices Virtex-5 Devices Understanding Timing Reports for GMII Setup/Hold Timing Non-Virtex-5 devices Virtex-5 devices with Delayed Data/Control Virtex-5 Devices with Delayed Clock Constraints when Implementing an External RGMII RGMII IOB Constraints = 8 - 6.134 = 1.866 ns = 7.554 - 8 = -0.446 ns RGMII Input Setup/Hold Timing Spartan-3, Spartan-3E, Spartan-3A, and Virtex-4 Devices Virtex-5 Devices RGMII DDR Constraints Understanding Timing Reports for RGMII Setup/Hold timing Non-Virtex-5 Devices Virtex-5 devices with delayed Data/Control Virtex-5 Devices with Delayed Clock = 8 - 7.179 = 0.821 ns = 8.893 - 8 = 0.893 ns = 0.893 ns tSETUP = 12 - 11.179 = 0.821 ns Page Chapter 10 Clocking and Resetting Clocking the Core With Internal GMII With External GMII With RGMII Multiple Cores With External GMII With RGMII Chapter 10: Clocking and Resetting Figure 10-4: Clock Management Logic with External RGMII (Multiple Cores) Figure 10-5: Reset Circuit for a Single Clock/reset Domain Reset Conditions Chapter 11 Interfacing to Other Cores Ethernet 1000Base-X PCS/PMA or SGMII Core Integration to Provide 1000BASE-X PCS with TBI Ethernet 1000Base-X PCS/PMA or SGMII Core Integration to Provide 1000BASE-X PCS and PMA using a RocketIO Tra n s c e i v e r 1-Gigabit Ethernet MAC LogiCORE Ethernet 1000BASE-X PCS/PMA or SGMII LogiCORE Virtex-4 GT11 RocketIO 0 0 Page Virtex-5 LXT and SXT Devices Chapter 11: Interfacing to Other Cores Virtex-5 FXT Devices Integration to Provide SGMII Functionality Ethernet Statistics Core Connecting the Ethernet Statistics Core to Provide Statistics Gathering Chapter 11: Interfacing to Other Cores Figure11-5 illustrates connecting the Ethernet Statistics core to the MAC. Figure 11-5: Interfacing the Ethernet Statistics to the 1-Gigabit Ethernet MAC Page Page Chapter 12 Implementing Your Design Pre-implementation Simulation Using the Simulation Model Synthesis XSTVHDL Implementation Generating the Xilinx Netlist Mapping the Design Placing-and-Routing the Design Static Timing Analysis Post-Implementation Simulation Generating a Simulation Model Using the Model Other Implementation Information Appendix A Using the Client-Side FIFO Interfaces Tra ns mit FI FO Receive FIFO Overview of LocalLink Interface Data Flow Functional Operation Clock Requirements Receive FIFO Tra ns mit FI FO VHDL Expanding Maximum Frame Size User Interface Data Width Conversion Appendix B Core Verification, Compliance, and Interoperability Verification by Simulation Hardware Verification Page Appendix C Calculating DCM Phase-Shifting DCM Phase-Shifting Finding the Ideal Phase-Shift Page Appendix D Core Latency Transmit Path Latency Receive Path Latency