Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Patent
1995-11-02
1998-04-14
Olms, Douglas W.
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
370438, 370448, H04L 12413
Patent
active
057401748
ABSTRACT:
An expansion bus is provided for use with bus systems of the type wherein only a single data signal or data packet may be transmitted over the bus at any one time, such as Ethernet bus systems. The expansion bus includes a set of repeater units each connected to a set of local transceivers respectively connected to remote bus masters, such as remote computers. The repeater units are interconnected by a single data bus. Collision detection and arbitration of usage of the single data line is achieved using a distributed symmetric arbitration system as follows. Each repeater unit has a dedicated activity line which is interconnected to each of the other repeater units. Each repeater unit also includes an identical arbitration unit connected to the respective activity lines. When a repeater unit receives data from a local transceiver for transmission onto the single data bus, the arbitration unit of the repeater unit asserts an activity signal onto the corresponding activity line. The arbitration unit then waits a predetermined time period before enabling transmission of data onto the single data bus. If, during that time period, any activity signals are detected on any of the other activity lines, then data transmission is not enabled. Rather, a global collision is detected and appropriate jam signals are transmitted to the remote computers providing the data indicating that the data is invalid and must be retransmitted. The predetermined delay period is at least equal to the maximum amount of time required for an activity signal to be transmitted to, and processed by, each of the other repeater units of the system. The arbitration units continue to monitor for activity signals throughout the duration of a data transmission and if any such activity signals are asserted, the data transmission is invalidated and may be terminated. Again, appropriate jam signals are transmitted to the remote computers. Method and apparatus embodiments of the invention are disclosed.
REFERENCES:
patent: 5311512 (1994-05-01), Bartis et al.
patent: 5345447 (1994-09-01), Noel
Cypress Semiconductor Corp.
Olms Douglas W.
Phillips Matthew C.
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