Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1997-12-03
2001-02-06
Wiley, David A. (Department: 2781)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C711S150000
Reexamination Certificate
active
06185646
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to computer systems with high-speed synchronous multi-drop busses, and more particularly, relates to a data transfer method and apparatus on a high-speed synchronous multi-drop bus.
DESCRIPTION OF THE RELATED ART
Synchronous multi-drop communication busses are a common element in computer systems today. Multiple devices attach to the bus, allowing any device to communicate with any other device. Each device can initiate transfers on the bus after first having gained permission via an arbitration protocol. As a device obtains ownership of the bus and begins to transfer data, due to the synchronous nature of the bus, the data must be able to propagate successfully to all other devices within each given clock cycle.
Due to the topology, or the physical relationship, of all the devices on this bus, some device-to-device propagation delays are shorter than others. As a result of reflections and other transmission-line effects of the wires, the propagation delays are the largest when a device is communicating with another device that is close in physical proximity. This is called near-end communication; that is, communicating with another device that is nearest. The propagation delays are the shortest when communicating with devices that are the farthest away. In designing a synchronous multi-drop bus, the limiting factor of how fast the clocking rate can be typically is determined by the propagation delay of the near-end communication paths.
A need exists to increase the clocking rate of the bus beyond the limit imposed by the near-end communication paths, but to still allow any-device to any-device communication.
SUMMARY OF THE INVENTION
Important objects of the present invention are to provide a data transfer method and apparatus on a high-speed synchronous multi-drop bus; to provide such method and apparatus substantially without negative effect; and to provide such method and apparatus that overcome many of the disadvantages of prior art arrangements.
In brief, a data transfer method and apparatus are provided for a computer system on a high-speed synchronous multi-drop bus. Multiple devices including at least a first group of a plurality of devices and a second group of at least one device are connected to the high-speed synchronous multi-drop bus. To transfer data between devices in the first group, a first unidirectional data valid signal is applied to each device in the second group. The data from a sending device in the first group is transferred to a designated device in the second group. A second unidirectional data valid signal is applied to each device in the first group. The data is transferred to a selected device in the first group.
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Barrett Wayne Melvin
Bartley Gerald Keith
Baska Douglas A.
Dahlen Paul Eric
Drehmel Robert Allen
International Business Machines - Corporation
Pennington Joan
Wiley David A.
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