Jack A Duke

44280467, Jan 24, 1984

May 5, 1980

6/146805

Venu Chari - San Diego CA
Jack R. Duke - San Marcos CA
Shimon Gersten - San Diego CA

NCR Corporation - Dayton OH

G06F 1516

364200

A data processing system having a plurality of subsystems linked by a star coupler. The star coupler includes contention circuitry for controlling the star coupler so that at any given time no more than one selected subsystem can pass a message through the star coupler. The contention circuitry uses a conventional priority encode circuit to determine the selected one of the subsystems, so that the first message to be received from one of the subsystems is the message passed or, if two or more messages are received from subsystems simultaneously, the message from the subsystem having the highest relative priority established by the priority encode circuit is the message passed. In an embodiment showing an expanded star coupler, the contention circuitry has plural first level contention circuits and a second level contention circuit, each using a conventional priority encode circuit.

40386449, Jul 26, 1977

Nov 19, 1975

5/633345

Jack R. Duke - Escondido CA
Philip W. Brooks - Lakeside CA
Robert R. Elzer - Escondido CA

NCR Corporation - Dayton OH

G06F 304
G06F 918

364900

In order to carry out data transfer among the subsystems of a bus oriented data processing system, each subsystem is coupled to the bus by a local bus adapter which controls both source and destination aspects of the information transfer. Each local bus adapter has a unique "busy" line which may be interrogated by any local bus adapter connected to the bus. When a source subsystem wishes to transfer information to a destination subsystem, the source local bus adapter determines from the destination local bus adapter's busy line whether or not the destination subsystem is available to accept the information. If the destination subsystem is available, the source local bus adapter requests access to the bus from priority resolution apparatus. When the source request is granted, the source local bus adapter issues the message to the bus and also sets the destination local bus adapter's busy line to designate the busy state which indicates to the destination bus adapter that it must prepare to receive a message and also indicates to all subsequently requesting local bus adapters that the particular subsystem to which information just placed on the bus is to be transferred is temporarily not available to receive information from any other local bus adapter. When the message has been received by the destination local bus adapter, both the source and destination local bus adapters enter a status cycle to check the integrity of the transmitted message.

44868553, Dec 4, 1984

Jan 28, 1982

6/343140

Jack R. Duke - San Marcos CA

NCR Corporation - Dayton OH

G06F 304

364900

An activity detector device detects the presence or absence of information transmission over a serial data link between a computer system and a peripheral device. If a presence of a data signal exists as determined by the activity detector, the data signal is transmitted through to the computer system. If an absence of the data signal exists as determined by the activity detector, the input transmission link is decoupled from the computer system by the activity detector and places an all ones signal on the input line to the computer system consistent with the I/O protocol.

41288831, Dec 5, 1978

Sep 30, 1977

5/838280

Jack R. Duke - San Marcos CA
Niranjan S. Shah - Escondido CA
William C. Woolf - San Diego CA

NCR Corporation - Dayton OH

G06F 304

364200

A data processing system includes a plurality of data handling subsystems which communicate with each other by means of an interval transfer bus. The subsystems are located at ports along the bus and each is provided with a local bus adapter interconnecting the subsystem with the bus. Busy lines are provided, one for each port on the bus, and all such busy lines are connected to all of the ports for use by any such port when the latter is acting as a source. Each busy line is uniquely connected to an individual one of the ports and is employed at such individual port to signal to all other ports the busy or available state of the individual port. A subsystem, acting as a source, inspects the busy line that is unique to the selected destination, and if availability of the selected destination subsystem is indicated by the state of its busy line, a request for access is issued by the source, and if granted, the source raises the distination busy line to busy state, and transmits its message. To enable two subsystems to share a common port and a common busy line without modification of other subsystems that use the internal transfer bus, a pair of shared local bus adapters is provided at a single port, each shared adapter being uniquely connected to a respective one of the two subsystems at such port. The shared local adapters are connected with each other so that the common busy line of the port is employed by the two to signal that either or both of the shared adapters are busy or are available.