Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1998-12-22
2001-06-26
Thai, Xuan M. (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S100000, C710S240000
Reexamination Certificate
active
06253269
ABSTRACT:
FIELD OF INVENTION
This invention relates in general to communications equipment. More particularly, it is directed to providing a communication device with the ability to switch or arbitrate between a plurality of communication buses.
BACKGROUND OF THE INVENTION
An electronic card chassis typically provides a number of card slots for inserting electronic equipment or application cards. These application cards are designed to perform functions such as providing modem card functions or other communication interface card functions. A communication backplane in the electronic card chassis provides the application cards a source of power and communication access through the card chassis. The communication backplane may include a plurality of different backplane communication buses to allow electronic circuit cards in the card chassis to communicate to external devices or to other cards in the card chassis.
In addition to the plurality of application cards capable of performing a variety of functions, the electronic card chassis may also contain a management card to perform system overhead management functions for the application cards in the chassis. A backplane communication bus allows the management card to communicate to the plurality of application cards. The communication bus provides management cards a communication path through the communication backplane to access each of the application cards in the card chassis.
To provide for fault tolerant operation, the card chassis may include a number of management cards for backup and redundancy in case of a failure of a primary management card. If a management card were to experience a failure, a second or backup management card could take over the management function of the application cards in the electronic card chassis.
In this redundant configuration including a plurality of management cards, each of the plurality management cards will typically have a backplane communication bus connection to each of the application cards. As a result of the plurality of management cards, each application card will have a plurality of backplane communication buses from which it may receive communications from the management cards at any time. As a consequence, the application card must be capable of receiving messages from any of the management cards over any one of the backplane communication buses accessing the card. Thus, to properly receive incoming management messages from any of the management cards, the application card must be able to dynamically switch between different backplane communication buses.
SUMMARY OF THE INVENTION
In accordance with an illustrative embodiment of the present invention, problems associated with managing communications from a plurality of different communication buses are addressed. The present embodiment allows application cards to arbitrate between messages on a plurality of different communication buses from devices communicating to the application card.
In the illustrative embodiment, the application card includes an arbiter that monitors the plurality of communication buses to determine which communication bus is allowed access to the application card. To this end, the arbiter monitors when a communication bus becomes active. When it detects a communication bus is active and no other mutually exclusive bus is active, the arbiter will allow that communication bus to access the application card. The communication bus can be switched to access the local bus of the application card. Once a communication bus is allowed access to the communication card, a hold off signal may be given to other communication buses accessing the application card. In addition, a timer may be utilized with the present embodiment to prevent a device from holding the communication bus to the application card for too long a period of time. It should be understood that the application card may be simultaneously accessed by a number of communication buses while other communication buses utilize mutually exclusive (one-at-a-time) access to the application card.
According to another aspect of the present invention, the arbiter allows the application card to dynamically select or arbitrate between different communication buses. The arbiter may include state machine logic to implement appropriate protocol of the communication bus. The arbiter can employ a variety of different algorithms to allow and control access to the application card. The arbiter may allow access to the application card according to the priority of different communication buses. The arbiter can allow simultaneous access to the application card according to the types and classes of different communication buses. Using the present invention, any arbitrary scheme for selecting among a plurality of communication buses may be implemented and dynamically tailored and changed according to the needs of the particular device.
The foregoing and other features and advantages of an illustrative embodiment of the present invention will be more readily apparent from the following detailed description, which proceeds with references to the accompanying drawings.
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Brown Steven R.
Cranston Michael T.
3Com Corporation
McDonnell & Boehnen Hulbert & Berghoff
Thai Xuan M.
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