Intel 82547xx, 82546GB-EB, 82545GM-EM, 82544GC-EI, 82541xx, 82540EP-EM User Manual
PCI/PCI-X Family of Gigabit Ethernet
Controllers Software Developer’s
Manual
82540EP/EM, 82541xx, 82544GC/EI, 82545GM/EM, 82546GB/EB, and
82547xx
317453006EN.PDF
Revision 4.0
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June 20063.2Updated Table 13.47. Changed the default setting of reserved bit 3 from 0b
April 20063.1Added bit definitions (bits 9:8) to PHY register PSCON (16d).
Nov 20053.0Updated Device Control/Status, EEPROM Flash Control & Data, Extended
July 20052.5Initial Public Release.
Updated Section 5 (added Table 5-15 “LED Configuration Defaults).
Updated section 8.7.4 “Discard PAUSE Frames and Pass MAC Control
Frames”.
Updated EEPROM Word 21h bit descriptions (section 5.6.18).
Updated Sections 13.4.30 and 13.4.31 (added text stating to use the
Interrupt Throttling Register (ITR) instead of registers RDTR and RADV for
applications requiring an interrupt moderation mechanism).
Added a note to sections 13.4.20 and 13.4.21 for the 82547Gi/EI.
Updated section 13.4.16.
Updated section 6.4.1. Changed acronym “WCR” to “WUC”.
Updated Table 13-87. Changed bit 24 settings to:
0b = Cache line granularity.
1b = Descriptor granularity.
to 1b.
Updated Figure 3.2 (added Receive Queue artwork).
Changed 81541ER-C0 to 82541ER-CO in Table 5-1.
Device Control, and TCTL register bit assignments.
Updated PHY register 00d - 03d, 07d, 09d, 17d - 21d, and 23d bit assign-
AAppendix (Changes From 82544EI/82544GC) ............................................393
BAppendix (82540EP/EM and 82545GM/EM Differences).........................395
Software Developer’s Manualxiii
Contents
Note:This page intentionally left blank.
xivSoftware Developer’s Manual
Introduction
Introduction1
1.1Scope
This document serves as a software developer’s manual for 82546GB/EB, 82545GM/EM,
82544GC/EI, 82541(PI/GI/EI), 82541ER, 82547GI/EI, and 82540EP/EM Gigabit Ethernet
Controllers. Throughout this manual references are made to the PCI/PCI-X Family of Gigabit
Ethernet Controllers or Ethernet controllers. Unless specifically noted, these references apply to all
the Ethernet controllers listed above.
1.2Overview
The PCI/PCI-X Family of Gigabit Ethernet Controllers are highly integrated, high-performance
Ethernet LAN devices for 1000 Mb/s, 100 Mb/s and 10 Mb/s data rates. They are optimized for
LAN on Motherboard (LOM) designs, enterprise networking, and Internet appliances that use the
Peripheral Component Interconnect (PCI) and PCI-X bus.
Note:The 82541xx and 82540EP/EM do not support the PCI-X bus.
The 82547GI(EI) connects to the motherboard chipset through a Communications Streaming
Architecture (CSA) port. CSA is designed for low memory latency and higher performance than a
comparable PCI interface.
The remaining Ethernet controllers provide a 32-/64-bit, 33/66 MHz direct interface to the PCI
Local Bus Specification (revision 2.2 or 2.3), as well as the emerging PCI-X extension to the PCI
Local Bus (revision 1.0a).
The Ethernet controllers provide an interface to the host processor by using on-chip command and
status registers and a shared host memory area, set up mainly during initialization. The controllers
provide a highly optimized architecture to deliver high performance and PCI/CSA/PCI-X bus
efficiency. By implementing hardware acceleration capabilities, the controllers enable offloading
various tasks such as TCP/UDP/IP checksum calculations from the host processor. They also
minimize I/O accesses and interrupts required to manage the Ethernet controllers and provide a
highly configurable design that can be used effectively in various environments.
The PCI/PCI-X Family of Gigabit Ethernet Controllers handle all IEEE 802.3 receive and transmit
MAC functions. They contain fully integrated physical-layer circuitry for 1000 Base-T, 100 BaseTX, and 10 Base-T applications (IEEE 802.3, 802.3u, and 802.3ab) as well as on-chip Serializer/
Deserializer (SerDes)
1
functionality that fully complies with IEEE 802.3z PCS.
1. The 82541xx, 82547GI/EI, and 82540EP/EM do not support any SerDes functionality.
Software Developer’s Manual1
Introduction
For the 82544GC/EI, when connected to an appropriate SerDes, it can alternatively provide an
Ethernet interface for 1000 Base-SX or LX applications (IEEE 802.3z).
Note:The 82546EB/82545EM is SerDes PICMG 2.16 compliant. The 82546GB/82545GM is SerDes
PICMG 3.1 compliant.
82546GB/EB Ethernet controllers also provide features in an integrated dual-port solution
comprised of two distinct MAC/PHY instances. As a result, they appear as multi-function PCI
devices containing two identically-functioning Ethernet controllers. See Section 12 for details.
1.3Ethernet Controller Features
This section describes the features of the PCI/PCI-X Family of Gigabit Ethernet Controllers.
• 64-bit addressing for systems with more than 4 GB of physical memory
• Efficient PCI bus master operation
• Command usage optimization for advanced PCI commands
1.3.2CSA Features (82547GI/EI Only)
• Uses dedicated port for client LAN controller directly on an MCH device
• High-speed interface with twice the peak bandwidth of a 32-bit 33 MHz PCI bus
• PCI power management registers recognized by the MCH
• Interface only uses 13 signals
1.3.3Network Side Features
• Auto-Negotiation and Link Setup
— Automatic link configuration including speed, duplex and flow control under IEEE
802.3ab for copper media
— For GMII/MII mode, the driver complies with the IEEE 802.3ab standard requirements
for speed, duplex, and flow control Auto-Negotiation capabilities
• Supports half and full duplex operation at 10 Mb/s and 100 Mb/s speeds while working with
the internal PHY
2Software Developer’s Manual
• IEEE 802.3x compliant flow control support
— Enables control of the transmission of Pause packets through software or hardware
triggering
— Provides indications of receive FIFO status
• State-of-the-art internal transceiver (PHY) with DSP architecture implementation
— Digital adaptive equalization and crosstalk
— Echo and crosstalk cancellation
— Automatic MDI/MDI-X crossover at all speeds and compensation for cable length
— Media Independent Interfaces (MII) IEEE 802.3e for supporting 10/10BASE-T
transceivers
• Integrated dual-port solution comprised of two distinct MAC/PHY instances (82546GB/EB)
• Receive and transmit IP and TCP/UDP checksum offloading capabilities
Introduction
• Transmit TCP Segmentation (operating system support required)
• Packet filtering based on checksum errors
• Support for various address filtering modes:
— 16 exact matches (unicast, or multicast)
— 4096-bit hash filter for multicast frames
— Promiscuous, unicast and promiscuous multicast transfer modes
• IEEE 802.1q VLAN support
— Ability to add and strip IEEE 802.1q VLAN tags
— Packet filtering based on VLAN tagging, supporting 4096 tags
1
• SNMP and RMON statistic counters
• Support for IPv6 including (not applicable to the 82544GC/EI):
— IP/TCP and IP/UDP receive checksum offload
— Wake up filters
— TCP segmentation
1. Not applicable to the 82541ER.
Software Developer’s Manual3
Introduction
1.3.5Additional Performance Features
• Provides adaptive Inter Frame Spacing (IFS) capability, enabling collision reduction in half
duplex networks (82544GC/EI)
• Programmable host memory receive buffers (256 B to 16 KB)
• Programmable cache line size from 16 B to 128 B for efficient usage of PCI bandwidth
• Implements a total of 64 KB (40 KB for the 82547GI/EI) of configurable receive and transmit
data FIFOs. Default allocation is 48 KB for the receive data FIFO and 16 KB for the transmit
data FIFO
• Descriptor ring management hardware for transmit and receive. Optimized descriptor fetching
and write-back mechanisms for efficient system memory and PCI bandwidth usage
• Provides interrupt coalescing to reduce the number of interrupts generated by receive and
transmit operations (82544GC/EI)
• Supports reception and transmission of packets with length up to 16 KB
• New intelligent interrupt generation features to enhance driver performance (not applicable to
the 82544GC/EI):
— Packet interrupt coalescing timers (packet timers) and absolute-delay interrupt timers for
both transmit and receive operation
— Short packet detection interrupt for improved response time to TCP acknowledges
— Transmit Descriptor Ring “Low” signaling
— Interrupt throttling control to limit maximum interrupt rate and improve CPU utilization
4Software Developer’s Manual
Introduction
1.3.6Manageability Features (Not Applicable to the 82544GC/EI or
82541ER)
• Manageability support for ASF 1.0 and AoL 2.0 by way of SMBus 2.0 interface and either:
register set and power down functionality supporting D0 and D3 states
• Supports Wake on LAN (WoL)
• Provides four wire serial EEPROM interface for loading product configuration information
— Allows use of either 3.3 V dc or 5 V dc powered EEPROM
• Provides external parallel interface for up to 512 KB of FLASH memory for support of Pre-
Boot Execution Environment (PXE)
• Provides seven general purpose user mode pins
• Provides Activity and Link LED indications
• Supports little-endian byte ordering for 32- and 64-bit systems
• Provides loopback capabilities under TBI (82544GC/EI)
EB and 82545GM/EM) and GMII/MII modes of operation
• Provides IEEE JTAG boundary scan support
• Four programmable LED outputs (Not applicable to the 82544GC/EI).
—For the 82546GB/EB, four programmable LED outputs for each port
• Detection and improved power-management with LAN cable unconnected (82546GB/EB)
1.3.8Technology Features
Implemented in 0.15 CMOS process (0.13 for the 82541xx and 82547GI/EI)
•
1
2
(internal SerDes for the 82546GB/
• Packaged in 364 PBGA.
—For the 82544EI, packaged in 416 PBGA.
—For the 82540EP/EM, 82541xx, and 82547GI/EI, packaged in 196 PBGA.
• Implemented in low power (3.3 V dc or 5 V dc compatible PCI signaling) CMOS process
1. Not applicable to the 82541ER.
2. Not applicable to the 82541xx, 82547GI/EI or 82540EP/EM.
Software Developer’s Manual5
Introduction
1.4Conventions
This document uses notes that call attention to important comments:
Note:Indicates details about the hardware’s operations that are not immediately obvious. Read these
notes to get information about exceptions, unusual situations, and additional explanations of some
PCI/PCI-X Family of Gigabit Ethernet Controller features.
1.4.1Register and Bit References
This document refers to Ethernet controller register names using all capital letters. To refer to a
specific bit in a register the convention REGISTER.BIT is used. For example, CTRL.ASDE refers
to the Auto-Speed Detection Enable bit in the Device Control Register (CTRL).
1.4.2Byte and Bit Designations
This document uses “B” to abbreviate quantities of bytes. For example, a 4 KB represents 4096
bytes. Similarly, “b” is used to represent quantities of bits. For example, 100 Mb/s represents 100
Megabits per second.
1.5Related Documents
• IEEE Std. 802.3, 2000 Edition. Incorporates various IEEE standards previously published
separately.
• PCI Local Bus Specification, Revision 2.2 and 2.3, PCI Local Bus Special Interest Group.
1.6Memory Alignment Terminology
Some PCI/PCI-X Family of Gigabit Ethernet Controller data structures have special memory
alignment requirements. This implies that the starting physical address of a data structure must be
aligned as specified in this manual. The following terms are used for this purpose:
• BYTE alignment: Implies that the physical addresses can be odd or even. Examples:
0FECBD9A1h, 02345ADC6h.
• WORD alignment: Implies that physical addresses must be aligned on even boundaries. For
example, the last nibble of the address can only end in 0, 2, 4, 6, 8, Ah, Ch, or Eh
(0FECBD9A2h).
• DWORD (Double-Word) alignment: Implies that the physical addresses can only be aligned
on 4-byte boundaries. For example, the last nibble of the address can only end in 0, 4, 8, or Ch
(0FECBD9A8h).
• QWORD (Quad-Word) alignment: Implies that the physical addresses can only be aligned on
8-byte boundaries. For example, the last nibble of the address can only end in 0 or 8
(0FECBD9A8h).
• PARAGRAPH alignment: Implies that the physical addresses can only be aligned on 16-byte
boundaries. For example, the last nibble must be a 0 (02345ADC0h).
6Software Developer’s Manual
Architectural Overview
Architectural Overview2
2.1Introduction
This section provides an overview of the PCI/PCI-X Family of Gigabit Ethernet Controllers. The
following sections give detailed information about the Ethernet controller’s functionality, register
description, and initialization sequence. All major interfaces of the Ethernet controllers are
described in detail.
The following principles shaped the design of the PCI/PCI-X Family of Gigabit Ethernet
Controllers:
1. Provide an Ethernet interface containing a 10/100/1000 Mb/s PHY that also supports 1000
Base-X implementations.
2. Provide the highest performance solution possible, based on the following:
— Provide direct access to all memory without using mapping registers
— Minimize the PCI target accesses required to manage the Ethernet controller
— Minimize the interrupts required to manage the Ethernet controller
— Off-load the host processor from simple tasks such as TCP checksum calculations
— Maximize PCI efficiency and performance
— Use mixed signal processing to assure physical layer characteristics surpass specifications
for UTP copper media
3. Provide a simple software interface for basic operations.
4. Provide a highly configurable design that can be used effectively in different environments.
The PCI/PCI-X Family of Gigabit Ethernet Controllers architecture is a derivative of the 82542
and 82543 designs. They take the MAC functionality and integrated copper PHY from their
predecessors and adds SMBus-based manageability and integrated ASF controller functionality to
the MAC
solution comprised of two distinct MAC/PHY instances.
1
. In addition, the 82546GB/EB features this architecture in an integrated dual-port
1.Not applicable to the 82544GC/EI or 82541ER.
Software Developer’s Manual7
Architectural Overview
MDI
Interface B
1000Base-T PHY Interfaces
Design for
Test Interface
External
TBI Interface
LEDsLEDs
Software
Defined Pins
Software
Defined Pins
EEPROM
Interface
SMBus
Interface
MDI
Interface A
Flash Interface
MDIO
GMII/
MII
MDIO
GMII/
MII
Device
Function 0
MAC/Controller
(LAN A)
Device
Function 1
MAC/Controller
(LAN B)
PCI (64-bit, 33/66 MHz)/PCI-X (133 MHz)
10/100/1000
PHY
10/100/1000
PHY
1000Base-T PHY Interface
Design for
Test Interface
External
TBI Interface
(
82545GM/EM only
)
LEDs
Software
Defined Pins
EEPROM
Interface
SMBus
Interface
MDI
Interface
Flash Interface
MDIO
GMII/
MII
Device
Function 0
MAC/Controller
PCI (64-bit, 33/66 MHz)/PCI-X (133 MHz)
Note: 82540EP/EM and 82541xx do not support PCI-X; 82544GC/EI and 82541ER do not support SMBus interface
10/100/1000
PHY
2.2External Architecture
Figure 2-1 shows the external interfaces to the 82546GB/EB.
Figure 2-1. 82546GB/EB External Interface
Figure 2-2 shows the external interfaces to the 82545GM/EM, 82544GC/EI, 82540EP/EM, and
82541xx.
8Software Developer’s Manual
Figure 2-2. 82545GM/EM, 82544GC/EI, 82540EP/EM, and 82541xx External Interface
Figure 2-3 shows the external interfaces to the 82547GI/EI.
Architectural Overview
Slave
Access
Logic
Control
Status
Logic
Statistics
CSA Port
TX/RX MAC
CSMA/CD
Trellis Viterbi
Encoder/Decoder
PCI CoreEEPROMFLASH
DMA Function
Descriptor Management
RX Filters
(Perfect,
Multicast,
VLAN)
VLA
N
8 bits
8 bits
Side-stream
Scrambler/
Descrambler
4 bits
4 bits
40KB
Packet
RAM
Management
Interface
PHY
Control
ECHO, NEXT,
FEXT
Cancellers
AGC, A/D
Timing
Recovery
Media Dependent Interface
4DPAM5
Encoder
Pulse Shaper,
DAC, Filter
Line DriverHybrid
Figure 2-3. 82547GI(EI) External Interface
Software Developer’s Manual9
Architectural Overview
PCI/
PCI-X
Core
PCI Interface
EEPROMFlash
DMA
Engine
Packet
Buffer
TX MAC
(10/100/
1000 Mb)
RX MAC
(10/100/
1000 Mb)
Packet/
Manageability
Filter
TX
Switch
ASF
Manageability
GMII/
MII
Link I/F
MDIO
MDIO
RMON
Statistics
SM Bus
Host Arbiter
2.3Microarchitecture
Compared to its predecessors, the PCI/PCI-X Family of Gigabit Ethernet Controller’s MAC adds
improved receive-packet filtering to support SMBus-based manageability, as well as the ability to
transmit SMBus-based manageability packets. In addition, an ASF-compliant TCO controller is
integrated into the controller’s MAC for reduced-cost basic ASF manageability.
Note:The 82544GC/EI and 82541ER do not support SMBus-based manageability.
For the 82546GB/EB, this new functionality is packaged in an integrated dual-port combination.
The architecture includes two instances of both the MAC and PHY along with a single PCI/PCI-X
interface. As a result, each of the logical LAN devices appear as a distinct PCI/PCI-X bus device.
The following sections describe the hardware building blocks. Figure 2-4 shows the internal
microarchitecture.
2.3.1PCI/PCI-X Core Interface
The PCI/PCI-X core provides a complete glueless interface to a 33/66 MHz, 32/64-bit PCI bus or a
33/66/133 MHz, 32/64 bit PCI-X bus. It is compliant w ith the PCI Bus Specifica tion Rev 2. 2 or 2.3
and the PCI-X Specification Rev. 1.0a. The Ethernet controllers provide 32 or 64 bits of addressing
and data, and the complete control interface to operate on a 32-bit or 64-bit PCI or PCI-X bus. In
systems with a dedicated bus for the Ethernet controller, this provides sufficient bandwidth to
support sustained 1000 Mb/s full-duplex transfer rates. Systems with a shared bus (especially the
32-bit wide interface) might not be able to maintain 1000 Mb/s, but can sustain multiple hundreds
of Mbps.
Figure 2-4. Internal Architecture Block Diagram
10Software Developer’s Manual
When the Ethernet controller serves as a PCI target, it follows the PCI configuration specification,
which allows all accesses to it to be automatically mapped into free memory and I/O space at
initialization of the PCI system.
When processing transmit and receive frames, the Ethernet controller operates as master on the PCI
bus. As a master, transaction burst length on the PCI bus is determined by several factors, including
the PCI latency timer expiration, the type of bus transfer being made, the size of the data transfer,
and whether the data transfer is initiated by receive or transmit logic.
The PCI/PCI-X bus interfaces to the DMA engine.
2.3.282547GI/EI CSA Interface
CSA is derived from the Intel® Hub Architecture. The 82547EI Controller CSA port consists of 11
data and control signals, two strobes, a 66 MHz clock, and driver compensation resistor connections. The operating details of these signals and the packet data protocol that accompanies them are
proprietary. The CSA port has a theoretical bandwidth of 266 MB/s — approximately twice the
peak bandwidth of a 32-bit 33 MHz PCI bus.
The CSA port architecture is invisible to both system software and the operating system, allowing
conventional PCI-like configuration.
Architectural Overview
2.3.3DMA Engine and Data FIFO
The DMA engine handles the receive and transmit data and descriptor transfers between the host
memory and the on-chip memory.
In the receive path, the DMA engine transfers the data stored in the receive data FIFO buffer to the
receive buffer in the host memory, specified by the address in the descriptor. It also fetches and
writes back updated receive descriptors to host memory.
In the transmit path, the DMA engine transfers data stored in the host memory buffers to the
transmit data FIFO buffer. It also fetches and writes back updated transmit descriptors.
The Ethernet controller data FIFO block consists of a 64 KB (40 KB for the 82547GI/EI) on-chip
buffer for receive and transmit operation. The receive and transmit FIFO size can be allocated
based on the system requirements. The FIFO provides a temporary buffer storage area for frames
as they are received or transmitted by the Ethernet controller.
The DMA engine and the large data FIFOs are optimized to maximize the PCI bus efficiency and
reduce processor utilization by:
• Mitigating instantaneous receive bandwidth demands and eliminating transmit underruns by
buffering the entire out-going packet prior to transmission
• Queuing transmit frames within the transmit FIFO, allowing back-to-back transmission with
the minimum interframe spacing
• Allowing the Ethernet controller to withstand long PCI bus latencies without losing incoming
data or corrupting outgoing data
• Allowing the transmit start threshold to be tuned by the transmit FIFO threshold. This
adjustment to system performance is based on the available PCI bandwidth, wire speed, and
latency considerations
Software Developer’s Manual11
Architectural Overview
• Offloading the receiving and transmitting IP and TCP/UDP checksums
• Directly retransmitting from the transmit FIFO any transmissions resulting in errors (collision
detection, data underrun), thus eliminating the need to re-access this data from host memory
2.3.410/100/1000 Mb/s Receive and Transmit MAC Blocks
The controller’s CSMA/CD unit handles all the IEEE 802.3 receive and transmit MAC functions
while interfacing between the DMA and TBI/internal SerDes/MII/GMII interface block. The
CSMA/CD unit supports IEEE 802.3 for 10 Mb/s, IEEE 802.3u for 100 Mb/s and IEEE 802.3z and
IEEE 802.3ab for 1000 Mb/s.
The Ethernet controller supports half-duplex 10/100 Mb/s MII or 1000 Mb/s GMII mode and all
aspects of the above specifications in full-duplex operation. In half-duplex mode, the Ethernet
controller supports operation as specified in IEEE 802.3z specification. In the receive path, the
Ethernet controller supports carrier extended packets and packets generated during packet bursting
operation. The 82554GC/EI, in the transmit path, also supports carrier extended packets and can
be configured to transmit in packet burst mode.
The Ethernet controller offers various filtering capabilities that provide better performance and
lower processor utilization as follows:
• Provides up to 16 addresses for exact match unicast/multicast address filtering.
• Provides multicast address filtering based on 4096 bit vectors. Promiscuous unicast and
promiscuous multicast filtering are supported as well.
• The Ethernet controller strips IEEE 802.1q VLAN tag and filter packets based on their VLAN
ID. Up to 4096 VLAN tags are supported
1
.
In the transmit path, the Ethernet controller supports insertion of VLAN tag information, on a
packet-by-packet basis.
The Ethernet controller implements the flow control function as defined in IEEE 802.3x, as well as
specific operation of asymmetrical flow control as defined by IEEE 802.3z. The Ethernet controller
also provides external pins for controlling the flow control function through extern al logic.
2.3.5MII/GMII/TBI/Internal SerDes Interface Block
The Ethernet controller provides the following serial interfaces:
• A GMII/MII interface to the internal PHY.
• Internal SerDes interface
82544GC/EI: The Ethernet controller implements the 802.3z PCS function, the AutoNegotiation function and 10-bit data path interface (TBI) for both receive and transmit
operations. It is used for 1000BASE-SX, -LX, and -CX configurations, operating only at 1000
Mb/s full-duplex. The on-chip PCS circuitry is only used when the link interface is configured
for TBI mode and it is bypassed in internal PHY modes.
1.Not applicable to the 82541ER.
2.Not applicable to the 82544GC/EI, 82540EP/EM, 82541xx, and 82547GI/EI.
2
(82546GB/EB and 82545GM/EM)/Ten Bit Interface (TBI)2 for the
12Software Developer’s Manual
Architectural Overview
Note:Refer to the Extended Device Control Register (bits 23:22) for mode selection (see Section 13.4.6).
The link can be configured by several methods. Software can force the link setting to AutoNegotiation by setting either the MAC in TBI
82545GM/EM), or the PHY in internal PHY mode.
The speed of the link in internal PHY mode can be determined by several methods:
mode (internal SerDes for the 82546GB/EB and
• Auto speed detection based on the receive clock signal generated by the PHY.
• Detection of the PHY link speed indication.
• Software forcing the configuration of link speed.
2.3.610/100/1000 Ethernet Transceiver (PHY)
The Ethernet controller provides a full high-performance, integrated transceiver for 10/100/
1000 Mb/s data communication. The physical layer (PHY) blocks are 802.3 compliant and capable
of operating in half-duplex or full-duplex modes.
Highlights of the PHY blocks are as follows:
• Data stream serializers and encoders. Encoding techniques include Manchester, 4B/5B and
4D/PAM5. These bl ocks also perform data scram bli ng for 100/1000 Mb/s transmission as a
technique to minimize radiated Electromagnetic Interference (EMI).
• A multi-mode transmit digital to analog converter, which produces filtered waveforms
appropriate for the 10BASE-T, 100BASE-TX or 1000BASE-T Ethernet standards.
• Receiver Analog-to-Digital Converter (ADC). The ADC uses a 125 MHz sampling rate.
• Receiver decoders. These blocks perform the inverse operations of serializers, encoders and
scramblers.
• Active hybrid and echo canceller blocks. The active hybrid and echo canceller blocks reduce
the echo effect of transmitting and receiving simultaneously on the same analog pairs.
• NEXT canceller. This unit removes high frequency Near End Crosstalk induced among
adjacent signal pairs.
• Additional wave shaping and slew rate control circuitry to reduce EMI.
Because the Ethernet controller is IEEE-compliant, the PHY blocks communicate with the MAC
blocks through an internal GMII/MII bus operating at clock speeds of 2.5 MHz up to 125 MHz.
The Ethernet controller also uses an IEEE-compliant internal Management Data interface to
communicate control and status information to the PHY.
2.3.7EEPROM Interface
The PCI/PCI-X Family of Gigabit Ethernet Controllers provide a four-wire direct interface to a
serial EEPROM device such as the 93C46 or compatible for storing product configuration
information. Several words of the data stored in the EEPROM are automatically accessed by the
Ethernet controller, after reset, to provide pre-boot configuration data to the Ethernet controller
before it is accessible by the host software. The remainder of the stored information is accessed by
various software modules to report product configuration, serial number and other parameters.
Software Developer’s Manual13
Architectural Overview
2.3.8FLASH Memory Interface
The Ethernet controller provides an external parallel interface to a FLASH device. Accesses to the
FLASH are controlled by the Ethernet controller and are accessible to software as normal PCI
reads or writes to the FLASH memory mapping area. The Ethernet controller supports FLASH
devices with up to 512 KB of memory.
Note:The 82540EP/EM provides an external interface to a serial FLASH or Boot EEPROM device. See
Appendix B for more information.
2.4DMA Addressing
In appropriate systems, all addresses mastered by the Ethernet controller are 64 bits in order to
support systems that have larger than 32-bit physical addressing. Providing 64-bit addresses
eliminates the need for special segment registers.
Note:The PCI 2.2 or 2.3 Specification requires that any 64-bit address whose upper 32 bits are all 0b
appear as a 32-bit address cycle. The Ethernet controller complies with the PCI 2.2 or 2.3
Specification.
PCI is little-endian; however, not all processors in systems using PCI treat memory as little-endian.
Network data is fundamentally a byte stream. As a result, it is important that the processor and
Ethernet controller agree about the representation of memory data. The default is little-endian
mode.
Descriptor accesses are not byte swapped.
The following example illustrates data-byte ordering for little endian. Bytes for a receive packet
There are no alignment restrictions on packet-buffer addresses. The byte address for the major
words is shown on the left. The byte numbers and bit numbers for the PCI bus are shown across the
top.
Destination address stored
internally as shown here
dest_addr[0]
Multicast bit
...55D500112233...XXX00AA
33...
001122
223300AA0011
00AA
Several registers store Ethernet addresses in the Ethernet controller. Two 32-bit registers make up
the address: one is called “high”, and the other is called “low”. For example, the Receive Address
Register is comprised of Receive Address High (RAH) and Receive Address Low (RAL). The least
significant bit of the least significant byte of the address stored in the register (for example, bit 0 of
RAL) is the multicast bit. The LS byte is the first byte to appear on the wire. This notation applies
to all address registers, including the flow control registers.
Figure 2-5 shows the bit/byte addressing order comparison between what is on the wire and the
values in the unique receive address registers.
Architectural Overview
Figure 2-5. Example of Address Byte Ordering
The address byte order numbering shown in Figure 2-5 maps to Table 2-2. Byte #1 is first on the
wire.
Table 2-2. Intel® Architecture Byte Ordering
IA Byte #1 (LSB)23456 (MSB)
Byte Value (Hex)00AA00112233
Note:The notation in this manual follows the convention shown in Table 2-2. For example, the address in
T able 2-2 indicates 00_AA_00_11_22_33h, where the first byte (00h_) is the first byte on the wire,
with bit 0 of that byte transmitted first.
Software Developer’s Manual15
Architectural Overview
2.6Interrupts
The Ethernet controller provides a complete set of interrupts that allow for efficient software
management. The interrupt structure is designed to accomplish the following:
• Make accesses “thread-safe” by using ‘set’ and ‘clear-on-read’ rather than ‘read-modify-write’
operations.
• Minimize the number of interrupts needed relative to work accomplished.
• Minimize the processing overhead associated with each interrupt.
Intel accomplished the first goal by an interrupt logic consisting of four interrupt registers. More
detail about these registers is given in sections 13.4.17 through 13.4.21.
• Interrupt Cause ‘Set’ and ‘Read’ Registers
The Read register records the cause of the interrupt. All bits set at the time of the read are autocleared. The cause bit is set for each bit written as a 1b in the Set register. If there is a race
between hardware setting a cause and software clearing an interrupt, the bit remains set. No
race condition exists on writing the Set register. A ‘set’ provides for software posting of an
interrupt. A ‘read’ is auto-cleared to avoid expensive write operations. Most systems have
write buffering, which minimizes overhead, but typically requires a read operation to
guarantee that the write operation has been flushed from the posted buffers. Without autoclear, the cost of clearing an interrupt can be as high as two reads and one write.
• Interrupt Mask ‘Set’ (Read) and ‘Clear’ Registers
Interrupts appear on PCI only if the interrupt cause bit is a 1b, and the corresponding interrupt
mask bit is a 1b. Software can block assertion of the interrupt wire by clearing the bit in the
mask register. The cause bit stores the interrupt event regardless of the state of the mask bit.
The Clear and Set operations make this register more “thread-safe” by avoiding a ‘readmodify-write’ operation on the mask register. The mask bit is set to a 1b for each bit written in
the Set register, and cleared for each bit written in the Clear register. Reading the Set register
returns the current value.
Intel accomplished the second goal (minimizing interrupts) by three actions:
• Reducing the frequency of all interrupts (see Section 13.4.17). Not applicable to the
82544GC/EI.
• Accepting multiple receive packets before signaling an interrupt (see Section 3.2.3)
• Eliminating (or at least reducing) the need for interrupts on transmit (see Section 3.2.7)
The third goal is accomplished by having one interrupt register consolidate all interrupt
information. This eliminates the need for multiple accesses.
Note that the Ethernet controller also supports Message Signaled Interrupts as defined in the PCI
2.2, 2.3, and PCI-X specifications. See Section 4.1.3.1 for details.
16Software Developer’s Manual
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