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1-Gigabit Ethernet MAC v8.5 User Guide www.xilinx.com 55
UG144 April 24, 2009
Overview of Flow Control
R
-- 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). Figure 6-2 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
- LogiCORE™ IP 1
- 1-Gigabit Ethernet 1
- MAC v8.5 1
- Revision History 3
- Table of Contents 5
- Appendix D: Core Latency 8
- Schedule of Figures 9
- UG144 April 24, 2009 10
- Schedule of Tables 13
- About This Guide 15
- Conventions 16
- Online Document 17
- List of Acronyms 17
- Introduction 19
- Specifications 20
- Technical Support 20
- Feedback 20
- Core Architecture 21
- Core Components 22
- Core Interfaces 23
- Client Side Interface 26
- Receiver Interface 27
- Flow Control Interface 27
- Physical Side Interface 29
- MDIO Interface 30
- Generating the Core 31
- Component Name 32
- Management Interface 32
- Address Filter 32
- Physical Interface 32
- Output Generation 33
- Designing with the Core 35
- Know the Degree of Difficulty 37
- Keep it Registered 38
- Use Supported Design Flows 38
- Chapter 5 39
- Frame Reception with Errors 41
- Client-Supplied FCS Passing 42
- VLAN Tagged Frames 42
- Disabled 43
- Receiver Statistics Vector 44
- Transmitting Outbound Frames 47
- Client Underrun 48
- Inter-Frame Gap Adjustment 49
- Transmitter Statistics Vector 50
- Using Flow Control 53
- Flow Control Basics 54
- Pause Control Frames 55
- Core-initiated Pause Request 56
- Pause Frame Reception Enabled 57
- Operation 59
- Chapter 6: Using Flow Control 60
- Chapter 7 61
- GMII Receiver Logic 63
- DCM Reset circuitry 64
- IOB LOGIC 66
- Virtex-4 Devices 67
- RGMII Receiver Logic 70
- Implementing External RGMII 71
- Using the MDIO interface 76
- Configuration and Status 77
- Configuration Registers 78
- Receiver Configuration 79
- Transmitter Configuration 80
- Flow Control Configuration 81
- MDIO Configuration 82
- Address Filter Configuration 82
- Accessing the Address Table 85
- LOCATION 86
- 31 : 0 47 : 32 86
- IDLE IDLE32 bits 87
- STA drives MDIO 87
- Constraining the Core 93
- MDIO Logic 94
- Flow Control 95
- Configuration 95
- "reset_dist_grp"; 96
- GMII Input Setup/Hold Timing 97
- Non-Virtex-5 devices 99
- RGMII IOB Constraints 101
- RGMII Input Setup/Hold Timing 102
- Virtex-5 Devices 103
- RGMII DDR Constraints 104
- Non-Virtex-5 Devices 105
- -- DISCONTINUED PRODUCT 108
- Clocking and Resetting 109
- Multiple Cores 110
- With RGMII 111
- Reset Conditions 112
- Interfacing to Other Cores 113
- Tra ns ce i ve r 115
- Virtex-5 LXT and SXT Devices 117
- Virtex-5 FXT Devices 118
- Ethernet Statistics Core 119
- Implementing Your Design 123
- Implementation 124
- Static Timing Analysis 125
- Generating a Bitstream 125
- Generating a Simulation Model 125
- Using the Model 126
- Using the Client-Side FIFO 127
- Interfaces 128
- Receive FIFO 129
- Data Flow 130
- Functional Operation 131
- Expanding Maximum Frame Size 132
- Interoperability 133
- Appendix C 135
- Core Latency 137
- Appendix D: Core Latency 138
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