lan9420/lan9420i快速以太网控制器基于PCI总线的系统

　　LAN9420/LAN9420i is a full-featured， Fast Ethernet controller which allows for the easy and cost-effective integration of Fast Ethernet into a PCI-based system. LAN9420/LAN9420i consists of a PCI Local Bus Specification Revision 3.0 compliant interface， DMA Controller， Ethernet MAC， and 10/100 Ethernet PHY.

　　LAN9420/LAN9420i provides full IEEE 802.3 compliance and all internal components support full/half-duplex 10BASE-T， 100BASE-TX， and manual full-duplex flow control. The descriptor based scatter-gather DMA supports usage of zero-copy drivers， effectively increasing throughput while decreasing Host load. The integrated IRQ deassertion timer allows a minimum IRQ deassertion time to be set， providing reduced Host load and greater control over service routines. Automatic 32-bit CRC generation/checking， automatic payload padding， and 2K jumbo packets （2048 byte） are supported.