Patent WO-9512946-A1 (WO)
Title: Configurable network interface controller
Inventor: LOHMEYER MICHAEL GLENN
IPC: H04L12/56
Filed: 1994-07-21
Abstract: The present invention is directed to several aspects of a system configurable Ethernet network interface controller. In accordance with the first aspect of the invention, the configurable network interface controller performs a selective FIFO backup operation to remove unwanted data from the FIFO after it has been determined that the data is no longer wanted. The operation does not require a FIFO reset or the need to search through the bad data looking for the next good data. The bad data is removed before any more good data is written into the FIFO. In accordance with another aspect of the invention, the configurable network interface controller provides for the automatic retransmission of collided Ethernet frames from a local RAM while observing two modes of operation: (1) retransmission of as much of the frame as possible without violating latency requirements and (2) first guaranteeing the safe retransmission of the first 64 bytes and then returning to observation of the latency requirements. In accordance with another aspect of the invention, the configurable network interface controller provides a user-programmable, two-level priority arbitration mechanism. The arbitration mechanism allows users to program their own priority settings. Within a single bus cycle, the arbiter attempts to determine who the next bus owner will be, first from the user programmed register. If a clear 'winner' is not found, a second 'default' level decides the success to the bus. In accordance with another aspect of the invention, the configurable network interface controller provides a mechanism for observing the present states of any internal state machine of the device. This feature saves debugging time for first silicon. In accordance with another aspect of the invention, the configurable network interface controller provides a dual-function encoded chip select signal. The encoded chip select signal serves both as a chip select for multiple devices and as an identification signal to a master controller. In accordance with another aspect of the invention, the configurable network interface controller provides a multi-chip FIFO extension protocol. Utilizing this protocol, FIFOs that are physically separated (e.g., in separate chips) can be made to operate as though they are a single FIFO. In accordance with another aspect of the invention, the configurable network interface controller provides for programmed ignore bits in address matching. Thus, partial filtering is possible to allow for 'don't care' bits within the address field. In accordance with another aspect of the invention, the configurable network interface controller provides for variable sized blocked address space by which it is possible to create a bus where multiple devices of different address space sizes can coexist on the same bus at the same time, the address space for each bus device being separate from the others. In accordance with another aspect of the invention, the configurable network interface controller architecture includes receive and transmit network statistics counters that support LME, MIB and RMON statistics. Because of the differences between IEEE, LME, MIB and RMON protocols, subsets of the statistics are made available.