General Description
The LAN91C100FD is designed to facilitate the implementation of first generation Fast Ethernet adapters and connectivity products. For this first generation of products, flexibility dominates over integration. The LAN91C100FD is a digital device that implements the MAC portion of the CSMA/CD protocol at 10 and 100 Mbps, and couples it with a lean and fast data and control path system architecture to ensure the CPU to packet RAM data movement does not cause a bottleneck at 100 Mbps.
Total memory size is 128 Kbytes, equivalent to a total chip storage (transmit plus receive) of 64 outstanding packets. The LAN91C100FD is software compatible with the LAN9000 family of products and can use existing LAN9000 drivers (ODI, IPX, and NDIS) in 16 and 32 bit Intel X86 based environments.
Memory management is handled using a unique MMU (Memory Management Unit) architecture and a 32-bit wide data path. This I/O mapped architecture can sustain back-to-back frame transmission and reception for superior data throughput and optimal performance. It also dynamically allocates buffer memory in an efficient buffer utilization scheme, reducing software tasks and relieving the host CPU from performing these housekeeping functions. The total memory size is 128 Kbytes (external), equivalent to a total chip storage (transmit and receive) of 64 outstanding packets.

Product Features
■ Dual Speed CSMA/CD Engine (10 Mbps and 100 Mbps)
■ Compliant with IEEE 802.3 100BASE-T Specification
■ Supports 100BASE-TX, 100BASE-T4, and 10BASE-T Physical Interfaces
■ 32 Bit Wide Data Path (into Packet Buffer Memory)
■ Support for 32 and 16 Bit Buses
■ Support for 32, 16 and 8 Bit CPU Accesses
■ Synchronous, Asynchronous and Burst DMA Interface Mode Options
■ 128 Kbyte External Memory
■ Built-In Transparent Arbitration for Slave Sequential Access Architecture
■ Early TX, Early RX Functions
■ Flat MMU Architecture with Symmetric Transmit and Receive Structures and Queues
■ MII (Media Independent Interface) Compliant MAC-PHY Interface Running at Nibble Rate
■ MII Management Serial Interface
■ Seven Wire Interface to 10 Mbps ENDEC
■ EEPROM-Based Setup
■ Full Duplex Capability