Integrated twisted pair filter with a secure RIC function

Details Integrated twisted pair filter with a secure RIC function Integrated twisted pair filter with a secure RIC function

1998-06-22

2001-02-06

Coulter, Kenneth R. (Department: 2758)

Multiplex communications

Communication techniques for information carried in plural...

Combining or distributing information via time channels

Reexamination Certificate

active

06185226

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to local area networks and, in particular, to repeater interface controller circuits for use in local area networks.
BACKGROUND
The term “local area network” or LAN, generally refers a communications system that provides interconnection among a number of independent computing stations within a small area. This small area is typically a single building or set of closely grouped buildings.
Some of the standards or protocols for implementing a LAN require a medium attachment unit (“MAU”) that couples the computing station to the physical medium implementing the interconnection. These standards typically require an attachment unit interface (“AUI”) for coupling the computing station or twisted pair interface (“TPI”) to the associated MAU.
A “repeater” can be used to couple together a number of nodes or hubs to extend the size of a LAN. The repeater typically includes at least one MAU for each node or hub coupled to the repeater so that signals can be passed to and from a node or hub to any other node or hub coupled to the repeater. Typically, the repeater synchronizes, amplifies and regenerates the signals as the signals are passed through to reduce data corruption.
For example, the 10BASE-T Ethernet standard uses twisted pair wiring to provide the interconnection between computing stations, with separate transmit and receive circuits. The 10BASE-T Ethernet standard is herein incorporated by reference in its entirety. Some conventional twisted pair repeaters use external filters and buffer drivers to transmit signals on each twisted pair. Because a repeater can have several MAUs (i.e., ports to several nodes or hubs), a filter and buffer driver is needed for each port, thereby increasing the repeater's size and cost. The external filters and drivers also generate a significant amount of electro-magnetic interference (“EMI”).
The 10BASE-T Ethernet standard also requires each MAU in the LAN to transmit a series of “link pulses” to confirm that the MAU is properly connected. Because each repeater has one or more MAUs, each repeater must generate link pulses between signals (i.e., data) retransmitted or received on each MAU's associated twisted pair interconnect wiring. In addition, the 10BASE-T Ethernet standard provides for data transmission in “packets” that include destination address, source address, type/length field, and a data field.
SUMMARY
According to the present invention, a repeater interface controller (“RIC”) integrated circuit with integrated filters and buffer drivers is provided for use in a repeater.
In one embodiment, the RIC uses two filters to filter link pulses and a data signal for a plurality of ports. The term “signal” is used in this context to mean a serial data stream. Thus, the RIC is able to concurrently provide a filtered link pulse to some ports and a filtered data signal to other ports. Further, because only two filters are used, the area required to implement the plurality of ports is reduced relative to conventional repeaters that use a filter for each port. As a result, integration of the filters and buffer drivers onto the RIC integrated circuit is made more practical, thereby reducing size, cost and EMI radiation.
In another embodiment, the RIC uses three filters to filter link pulses, a Manchester encoded transmit data signal and a security data signal for twelve ports. Thus, the RIC is able to concurrently provide a filtered link pulse to some ports, a filtered Manchester encoded transmit data signal to other ports and a filtered security data signal to still other ports. Further, because only three filters are used, the area required to implement the plurality of ports is reduced relative to conventional repeaters, thereby making more practical the integration of the filters and buffer drivers. Accordingly, data security is provided and the size, cost and EMI radiation of the repeater is greatly reduced.
In another embodiment of the present invention, a RIC includes a logic circuit and a plurality of analog multiplexers and twisted pair buffer drivers. The analog multiplexers receive signals on their input lines and select which of these signals are passed to the buffer drivers to be outputted. The logic circuit provides control signals to the analog multiplexers such that the analog multiplexers select a new input line when the signal on the new input line is approximately the same as the signal on the currently selected input line. As a result, the signal passed on to the buffer drivers remains approximately the same, thereby preventing the switching noise, reflections and ground bounce that could be generated if the signals were not approximately the same.


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