Hub controller for providing deterministic access to CSMA local area network
First Claim
1. A hub controller for use with a carrier-sense-multiple access (CSMA) protocol local area network (LAN) having a plurality of user nodes each of which inhibit transmission of messages from the user node when the user node senses a carrier signal in accordance with the CSMA protocol, the hub controller comprising:
- a plurality of ports, each port connected to a common bus internal to the hub controller and to a user node external to the hub controller that generates and receives messages in accordance with the CSMA protocol, each port including;
media a control logic means for selectively controlling whether a pseudo carrier control signal which simulates the carrier signal in accordance with the CSMA protocol is presented to the user node connected to that port; and
control means operably connected to each of the media control logic means for determining which of the ports will present the pseudo carrier control signal,such that the hub controller can selectively generate the pseudo carrier control signal to each port and thereby inhibit the transmission of any messages from the user node connected to that port.
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Abstract
A method and apparatus for deterministic access to a carrier-sense-multiple-access (CSMA) or carrier-sense-multiple-access with collision detection (CSMA/CD) local area network (LAN) alters the basic indeterminate contention algorithm of the CSMA/CD protocol LAN within a hub controller. The hub controller includes media control logic that can selectively raise a pseudo carrier control signal to each port, thereby inhibiting any CSMA/CD protocol LAN transmissions by that port. In this way, the media control logic allows the hub controller to control which of the multiple ports will be allowed to contend for access to a common internal bus within the hub controller and for how long. A variety of different deterministic contention algorithms can be implemented by the hub controller, such as sequential polling, interrupt allocation, or a combination of deterministic contention algorithms with the normal CSMA/CD indeterminate contention algorithm.
137 Citations
17 Claims
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1. A hub controller for use with a carrier-sense-multiple access (CSMA) protocol local area network (LAN) having a plurality of user nodes each of which inhibit transmission of messages from the user node when the user node senses a carrier signal in accordance with the CSMA protocol, the hub controller comprising:
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a plurality of ports, each port connected to a common bus internal to the hub controller and to a user node external to the hub controller that generates and receives messages in accordance with the CSMA protocol, each port including; media a control logic means for selectively controlling whether a pseudo carrier control signal which simulates the carrier signal in accordance with the CSMA protocol is presented to the user node connected to that port; and control means operably connected to each of the media control logic means for determining which of the ports will present the pseudo carrier control signal, such that the hub controller can selectively generate the pseudo carrier control signal to each port and thereby inhibit the transmission of any messages from the user node connected to that port. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for selectively controlling access to a hub controller that interconnects a plurality of user nodes operating on a carrier-sense-multiple-access (CSMA) protocol local area network (LAN) having a plurality of user nodes each of which inhibit transmission of messages from the user node when the user node senses a carrier signal in accordance with the CSMA protocol to a common internal bus within the hub controller, the hub controller including a computer processor, the method comprising the computer-implemented steps of:
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selectively inhibiting transmission of any messages in accordance with the CSMA protocol from selected user nodes according to a preselected deterministic contention algorithm by selectively generating a pseudo carrier control signal that simulates the carrier signal to each of the selected user nodes to prevent those user nodes from initiating transmission of any messages in accordance with the CSMA protocol; and selectively allowing transmission of messages in accordance with the CSMA protocol from selected user nodes according to the preselected deterministic contention algorithm by selectively not generating the pseudo carrier control signal to each of the selected user nodes, such that the computer processor implements the deterministic contention algorithm without any modifications to the CSMA protocol as implemented within the user nodes. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification