Communication node with a first bus configuration for arbitration and a second bus configuration for data transfer

• US 5,579,486 A
• Filed: 01/14/1993
• Issued: 11/26/1996
• Est. Priority Date: 01/14/1993
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Van Brunt, Roger W., Oprescu, Florin
• Primary Examiner(s): Donaghue, Larry D.
• Application Number:
  US08/004,431
• Time in Patent Office: 1,412 Days
• Field of Search: 395/325, 395/800, 395/200, 395/275, 395/200.15, 395/200.13, 395/200.02, 395/831, 395/287, 395/299, 340/825.5, 340/825.03, 340/825.02, 370/85.1, 370/85.3, 370/63, 370/87.13
• US Class Current: 710/107
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/325 Power saving in peripheral device

Abstract

A node for a communication system that has a plurality of nodes, each of which may be coupled to a local host. The nodes are coupled between themselves in a tree topology by a plurality of point-to-point links. The interconnected nodes provide a first bus configuration for arbitration like a single bus. Following arbitration, the interconnected nodes provide a second configuration for high speed unidirectional data transfer without the bandwidth limitations of a single bus. Each node includes an arbiter, a data bus, a plurality of ports, a first multiplexer to select either the arbiter or the data bus, and a second multiplexer to select either the arbiter or the data bus. The data bus includes a transmit bus and a receive bus that are coupled with a repeater circuit that can resynchronize the data. During arbitration, the multiplexers select the arbiter to provide the function of a single bus for all the nodes. During data transfer, the multiplexers are configured for transmission of data. Furthermore, a node can function as a repeater and resynchronizer even if it is not connected to a local host or if the local host is turned off or otherwise nonoperational.

Claims

1. A communication system for interconnecting a plurality of local hosts, the communication system providing a first bus configuration for arbitration and a second bus configuration for unidirectional data transfer, comprising:

a plurality of nodes, each node including an arbiter, a data bus, at least one port, and at least one multiplexer responsive to said arbiter for selectively coupling each port of the node to one of the arbiter and the data bus;

a plurality of point-to-point links, each point-to-point link coupling a port of a first node with a port of a second, different node, so that the nodes have a tree topology coupled by said point-to-point links;

a plurality of local hosts, each local host being coupled to one of the nodes for arbitrating bus access, receiving data, and transmitting data; and

wherein in the first bus configuration the multiplexers couple the arbiters to the ports to receive and transmit arbitration messages thereon, and in the second bus configuration the multiplexers couple the data bus to the ports to selectively receive and transmit data thereon.

2. The communication system of claim 1 wherein at least one of the point-to-point links includes a connector cable having a first signal line for communicating a first signal and a second signal line for communicating a second signal.

3. The communication system of claim 2 wherein the connector cable further comprises a first power line for transferring power between nodes.

4. The communication system of claim 3 wherein each of the ports coupled to the connector cable comprises a transceiver having a transmitter and a receiver, said first signal is coupled to the transmitter, and the second signal is coupled to the receiver.

5. The communication system of claim 4 wherein the at least one multiplexer of each node comprises:

a set of first multiplexers responsive to the arbiter, each of the set of first multiplexers for selectively coupling the receiver in each port of the node to one of the arbiter and the data bus, and

a set of second multiplexers responsive to the arbiter, each of the set of second multiplexers for selectively coupling the transmitter in each port of the node to one of the arbiter and the data bus.

6. The communication system as claimed in claim 5, wherein the data bus in at least one node comprises:

a transmit bus coupled to the set of second multiplexers for supplying data to the ports;

a receive bus coupled to the set of first multiplexers for receiving data from the ports; and

coupling means for coupling the receive bus to the transmit bus.

7. The communication system as claimed in claim 6, wherein the coupling means includes a repeater circuit.

8. The communication system as claimed in claim 7 wherein the repeater circuit includes means for resynchronizing data.

9. The communication system of claim 2 wherein each of the ports coupled to the connector cable comprises a first transceiver having a transmitter and a receiver and a second transceiver having a transmitter and a receiver, and the first signal is coupled to the first transceiver and the second signal is coupled to the second transceiver.

10. The communication system of claim 9 wherein the arbiter includes transceiver control logic coupled to the first and second transceivers for controlling the direction of signal flow through each of the transceivers.

11. The communication system of claim 9 wherein each node further comprises:

a set of first multiplexers responsive to the arbiter, each of the set of first multiplexers for selectively coupling the first transceiver of each port of the node to one of the arbiter and the data bus, and

a set of second multiplexers responsive to the arbiter, each of the set of second multiplexers for selectively coupling the second transceiver in each port of the node to one of the arbiter and the data bus.

12. The communication system as claimed in claim 11, wherein the data bus in at least one node comprises:

a transmit bus coupled to said second multiplexers for supplying data to the ports;

a receive bus coupled to said first multiplexers for receiving data from the ports; and

coupling means for coupling the receive bus to the transmit bus.

13. The communication system as claimed in claim 11, wherein the coupling means includes a repeater circuit.

14. The communication system as claimed in claim 13 wherein the repeater circuit includes means for resynchronizing data.

15. A communication node for performing arbitration and data transmission between a plurality of like nodes, each node being coupled to at least one other node by a point-to-point communication link, the communication node providing a first bus configuration in which the bus appears as a single logical bus for arbitration and a second bus configuration in which the bus is configured for unidirectional data transmission, the communication node comprising:

a plurality of communication ports, each port coupled to one of the point-to-point communication links, each port having a transceiver including a receiver and a transmitter;

an arbiter coupled to each of the communication ports;

a data bus coupled to each of the communication ports; and

a plurality of first multiplexers, each first multiplexer being coupled to one of the receivers, each first multiplexer being selectable by the arbiter to couple the receiver to one of the data bus and the arbiter;

a plurality of second multiplexers, each second multiplexer being coupled to one of the transmitters, each second multiplexer being selectable by the arbiter to couple the transmitter to one of the data bus and the arbiter,

wherein in the first bus configuration the arbiter is coupled to the communication ports to receive and transmit arbitration messages thereon, and in the second bus configuration the ports are coupled to the data bus to selectively receive and transmit data thereon.

16. The communication node as claimed in claim 15, wherein the data bus comprises:

a transmit bus coupled to the local host and the second multiplexers for supplying data to the ports;

a receive bus coupled to the local host and said first multiplexers for receiving data from the port; and

coupling means for coupling the receive bus to the transmit bus.

17. The communication node as claimed in claim 16, wherein the coupling means includes a repeater circuit.

18. The communication node as claimed in claim 17 wherein the repeater circuit includes means for resynchronizing data.

19. A communication node for performing arbitration and data transmission between a plurality of like nodes, each node being coupled to a local host and coupled to at least one other node by a point-to-point communication link having a first signal line for communicating a first signal and a second signal line for communicating a second signal, the communication node providing a first bus configuration in which the bus appears as a single logical bus for arbitration and a second bus configuration in which the bus is configured for unidirectional data transmission, said communication node comprising:

a plurality of communication ports, each port coupled to the first signal line and the second signal line, each port having a transceiver including a receiver coupled to the first signal line and a transmitter coupled to the second signal line;

an arbiter coupled to the local host and each of the communication ports to control the direction of signal flow through the ports;

a transmit bus coupled to the local host and the ports for supplying data to the ports;

a receive bus coupled to the local host and the ports for receiving data from the ports;

a data repeater circuit coupled between the transmit bus and the receive bus;

a plurality of first multiplexers, each first multiplexer being coupled to one of the receivers, each first multiplexer being selectable by the arbiter to couple the receiver to one of the receive bus and the arbiter;

a plurality of second multiplexers, each second multiplexer being coupled to one of the transmitters, each second multiplexer being selectable by the arbiter to couple the transmitter to one of the transmit bus, the receive bus, and the arbiter; and

wherein in the first bus configuration the arbiter is coupled to said first and second multiplexers to receive and transmit arbitration messages thereon, and in the second bus configuration the first multiplexer is coupled to the receive bus to receive data, and the second multiplexer is coupled to the transmit bus to transmit data thereon.

20. A communication node for performing arbitration and parallel data transmission between a plurality of like nodes, each node being coupled to a local host and also coupled to at least one other node by a point-to-point communication link having a first signal line for communicating a first signal and a second signal line for communicating a second signal, the communication node providing a first bus configuration in which the bus appears as a single logical bus for arbitration and a second bus configuration in which the bus is configured for unidirectional, parallel data transmission, the communication node comprising:

a plurality of communication ports, each port coupled to the first signal line and the second signal line, each port having a first transceiver coupled to the first signal line, the first transceiver including a first receiver and a first transmitter, each port also having a second transceiver coupled to the second signal line, the second transceiver including a second receiver and a second transmitter;

an arbiter coupled to the local host, the arbiter including arbitration control logic responsive to signals on the first and second signal lines on each port of the node;

a first transmit bus coupled to the local host;

a second transmit bus coupled to the local host;

a first receive bus coupled to the local host;

a second receive bus coupled to the local host;

a first data repeater circuit coupled between the first transmit bus and the first receive bus;

a second data repeater circuit coupled between the second transmit bus and the second receive bus;

a plurality of first multiplexers, each of said first multiplexers being coupled to one of the first transceivers in the node, each first multiplexer being selectable to couple the first transceiver to one of the first receive bus, the first transmit bus, and the arbiter;

a plurality of second multiplexers, each of the second multiplexers being coupled to one of said second transceivers in the node, each second multiplexer being selectable to couple said second transceiver to one of the second receive bus, the second transmit bus, and the arbiter; and

wherein the arbiter is coupled to said first and second multiplexers, and further includes multiplexer control logic to select the coupling by the multiplexer, and further, wherein the arbiter is coupled to said first and second transceivers, and includes transceiver control logic to select the direction of signal flow through each of the transceivers.