SMSC LAN9420 - Manual (Page 53)

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
SMSC LAN9420/LAN9420i 53 Revision 1.22 (09-25-08)
DATASHEET
3.5 10/100 Ethernet MAC
The Ethernet Media Access Controller (MAC) provides the following features:
„ Compliant with the IEEE 802.3 and 802.3u specifications
„ Supports 10-Mbps and 100-Mbps data transfer rates
„ Transmit and receive message data encapsulation
„ Framing (frame boundary delimitation, frame synchronization)
„ Error detection (physical medium transmission errors)
„ Media access management
„ Medium allocation (collision detection, except in full-duplex operation)
„ Contention resolution (collision handling, except in full-duplex operation)
„ Decoding of control frames (PAUSE command) and disabling the transmitter
„ Generation of control frames
„ Internal MII interface for communication with the embedded PHY
„ Supports Virtual Local Area Network (VLAN) operations
„ Supports both full- and half-duplex operations
„ Support of CSMA/CD Protocol for half-duplex Mode
„ Supports flow control for full-duplex operation
„ Wake detection logic, which detects Wakeup Frames and Magic Packets
„ Collision detection and auto retransmission on collisions in Half-Duplex Mode
„ Preamble generation and removal
„ Automatic 32-bit CRC generation and checking
„ Options to insert PAD/CRC32 on transmit
„ Options to set Automatic Pad stripping in Receive packets
„ Checksum offload engine for calculation of layer 3 transmit and receive checksum
The MAC block includes a MAC Interface Layer (MIL). The MIL provides a FIFO interface between the
DMAC and the MAC. The MIL provides the following features:
„ Provides a bridge between the DMA controller and Ethernet MAC
„ Separate paths for transmit and receive operations
„ Separate 2KB FIFOs (one for Transmit and one for Receive operations)
„ Receive: Sends only filtered packets to DMAC
„ Transmit: Supports Store and Forward mechanism
„ Transmit: Frame data held in MIL FIFO until the MAC retransmits the packets without collision
The MAC incorporates the essential protocol requirements for operating an Ethernet/IEEE 802.3-
compliant node and provides an interface between the Host system and the internal Ethernet PHY.
The MAC can operate in either 100-Mbps or 10-Mbps mode.
The MAC operates in both half-duplex and full-duplex modes. When operating in half-duplex mode,
the MAC complies fully with Section 4 of ISO/IEC 8802-3 (ANSI/IEEE standard) and ANSI/IEEE 802.3
standards. When operating in full-duplex mode, the MAC complies with IEEE 802.3x full-duplex
operation standard.
The MAC provides programmable enhanced features designed to minimize Host supervision, bus
utilization, and pre- or post-message processing. These features include the ability to disable retries
after a collision, dynamic FCS (Frame Check Sequence) generation on a frame-by-frame basis,
automatic pad field insertion and deletion to enforce minimum frame size attributes, and automatic