Computer interconnect system with transmit-abort function

• US 5,020,020 A
• Filed: 04/07/1989
• Issued: 05/28/1991
• Est. Priority Date: 04/07/1989
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Digital Equipment Corporation (HP Inc.)
• Inventors: Pomfret, Stephen T., Boaen, Yerell, Lary, Richard
• Primary Examiner(s): Shaw, Gareth D.
• Assistant Examiner(s): Loomis, John C.
• Application Number:
  US07/335,130
• Time in Patent Office: 781 Days
• Field of Search: 364/200, 364/900, 370/60, 370/94.1
• US Class Current: 709/235
• CPC Class Codes: H04L 12/44 Star or tree networks

Abstract

A computer interconnect system uses packet data transmission over serial links connecting nodes of a network. The serial links may provide simultaneous dual paths for transmit/receive. An adapter couples a CPU or the like at a node to the serial link. The adapter includes a packet memory for temporarily storing transmit packets and receive packets, along with a port processor for executing the protocol. Packets of data are transferred between the system bus of the CPU and the packet memory by a pair of data movers, one for read and one for write. All of the serial links of the system are connected to a distribution hub which forwards a transmitted packet to a destination node based upon an address sent with the packet. If the path to the destination node is busy, the hub returns a "flow control" signal to the source node, and in response to this signal the transmitted packet is aborted so that time on the network is not wasted by needless transmission that must be discarded.

Claims

1. A computer interconnect system for packet data transmission between a first node and a second node by an intermediate node, comprising:

(a) transmit/receive means at said first node coupled by a path to said second node for transmitting a packet to said second node via said intermediate node or for receiving a packet at said first node, said transmit/receive means including means for aborting transmission of a packet before the packet ends when said intermediate node signals by a flow control signal directed to said first node that said packet can not be successfully forwarded by said intermediate node to said second node;

(b) packet buffer means for temporarily storing packets of data received from said path or to be transmitted on said path;

(d) coupling means for transferring packets between said transmit/receive means and said packet buffer means;

(e) processor means, and data transfer means for transferring a packet from said processor means to said packet buffer means before transmission by said transmit/receive means, and for transferring a packet from said packet buffer means to said processor means after receiving said packet by said transmit/receive means.

2. Apparatus according to claim 1 wherein said path includes a serial data-transmit path and a serial data-receive path.

3. Apparatus according to claim 1 wherein said packets include a destination address and a source address.

4. Apparatus according to claim 1 wherein said intermediate node includes a distribution hub for selectively forwarding said packets to one of a plurality of second nodes, said hub being connected to said path, and said hub includes means for sending said flow control signal to said means for aborting.

5. Apparatus according to claim 4 wherein said means for sending is responsive to a busy condition of a path to a destination of said packet.

6. Apparatus according to claim 5 wherein said path has a transmit-data line and a receive-data line, and wherein said signal is sent by said receive-data line.

7. Apparatus according to claim 6 wherein said transmit/receive means includes means responsive to said signal.

8. Apparatus according to claim 7 wherein each one of said nodes has two of said paths to other nodes.

9. In a method of transmitting data between a number of nodes via an intermediate node in a computer interconnect system, the steps of:

(a) transmitting a packet from one of said nodes over a data path directed to another of said nodes via said intermediate node;

(b) detecting at said intermediate node a condition of said packet being transmitted and said packet failing to reach said another of said nodes while said step of transmitting is occurring, and sending a signal from said intermediate node to said one of said nodes representing said condition;

(c) and aborting said step of transmitting before all of said packet has been transmitted upon receipt of said signal.

10. A method according to claim 9 wherein said step of transmitting is bit-serial on said path, and wherein said packet includes source and destination addresses.

11. A method according to claim 10 wherein said intermediate node is a distribution hub, and including the steps of detecting said packet at said distribution hub and determining if a path to a destination node defined by said destination address is free or busy.

12. A method according to claim 11 including the step of sending said signal from said distribution hub to said one of said nodes if said path to said destination node is busy.

13. A method according to claim 9 including the step of sending said signal by said data path to indicate said condition from said intermediate node to said one node.

14. A method according to claim 13 wherein said signal is sent to said one node on a path separate from said transmission of said packet.

15. A computer interconnect adapter for packet data transmission at a node in a network, comprising:

(a) means in said adapter for transmitting a packet from said node over a transmit path directed to a selected remote node;

(b) means in said adapter responsive to a busy signal received on a receive path from an intermediate node upon a condition of said intermediate node being unsuccessful in forwarding said packet to said selected remote node, said signal being received while said packet is being transmitted;

(c) said means for transmitting including means for aborting said transmitting of said packet if said busy signal is received.

16. A device according to claim 15 wherein said network has serial data-transfer paths and includes a data-transmit path and a data-receive path.

17. A device according to claim 16 wherein said packet includes a destination address and a source address, and wherein said means responsive to a busy signal receives a signal on said data-receive path if said intermediate node is unsuccessful in forwarding said transmitted packet to said selected node as defined by said destination address.

18. A device according to claim 15 wherein said node is one of a plurality of nodes in a network, and said network includes a distribution hub coupled to paths to all of said plurality of nodes.

19. A device according to claim 18 wherein said means responsive to a busy signal receives said busy signal from said distribution hub.

20. A device according to claim 19 wherein said signal from said distribution hub is coupled to said means responsive to a busy signal by a receive-data line of said path.