DFE-500TX Ethernet PC Card User's Guide
Startup communication between the two devices occurs when both devices are power-on, the cable connection between them is good, and the Network Operating System software is running. As soon as those conditions are satisfied, the preparatory process of Autonegotiation between the DFE-500TX and its supporting hub proceeds automatically. If the hub has Autonegotiation functionality, then it and the DFE-500TX exchange a series of messages in which each device signals its capabilities and listens for corresponding information about the other. The Autonegotiation process requires only a few milliseconds, and the two devices select the best communication parameters supported by both devices.
If the hub does not have Autonegotiation functionality, then its monotone (single capability) message will be recognized by the DFE-500TX’s Autonegotiation facility, and the DFE-500TX will simply switch to the one of its own capabilities which matches that of the hub.
When the preparatory procedure of Autonegotiation is completed, then the line is ready and will provide a data channel which is optimal for the two devices. The line will remain ready without further Autonegotiation action until the linkage is broken. Autonegotiation then reoccurs at any time that the linkage is restored, again making the line ready for optimal data communications.
About PCI Bus
Your DFE-500TX Adapter delivers outstanding performance by fully exploiting the advanced features of your computer’s PCI bus. DFE-500TX Adapters utilize the Bus Master Mode of the PCI bus, allowing direct transfers of Ethernet packet content between computer memory and the adapter’s controller, thus minimizing network demand on the CPU. The adapter’s controller function is implemented by a DEC (Digital Equipment Corporation) Intelligent Ethernet Controller chip, which provides the additional benefit of reduced command processing overhead.
The working relationship between a DFE-500TX adapter and main memory working in Bus Master mode is powered by the Bridge/Memory Controller of the PCI bus. This reduces the CPU role in network operations, thus freeing the CPU to service other tasks, with resulting improvement in overall computing (multitasking) performance. At the same time, it produces superior network
