Event driven communication network

• US 5,499,374 A
• Filed: 11/22/1993
• Issued: 03/12/1996
• Est. Priority Date: 03/06/1992
• Status: Expired due to Term

• Current Assignee: Pitney Bowes Incorporated (Böwe Systec AG)
• Original Assignee: Pitney Bowes Incorporated (Böwe Systec AG)
• Inventors: Ryan, Frederick W. Jr., Di Giulio, Peter C., Riley, David W., Lee, David K.
• Primary Examiner(s): Harvey, Jack B.
• Assistant Examiner(s): Sheikh, Ayaz R.
• Application Number:
  US08/155,496
• Time in Patent Office: 841 Days
• Field of Search: 395/325, 395/200, 395/550, 395/725, 395/287, 395/728, 370/67, 370/95.1, 370/85.1, 370/85.8, 370/95.2
• US Class Current: 710/240
• CPC Class Codes: G06F 13/372 using a time-dependent priority, e.g. individually loaded time counters or time slot
• CPC Class Codes: H04L 12/4015 by scheduling the transmission of messages at the communication node
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A cost-effective motion control system communication architecture is provided that supports a centralized control node, distributed control nodes, and smart I/O peripheral control nodes. Networks designed using this architecture, which employs a serial bus, may be readily modified or expanded. The architecture supports both real-time highly periodic communications and event-driven peer-to-peer communications.

Claims

1. A communication network comprising:

a) a bus

b) a plurality of control nodes responsive to predetermined events to transmit messages on said bus, wherein a possibility of contention among said nodes exists;

c) a central node for transmitting an access control signal on said bus, said access control signal being followed by a contention avoiding time period, said time period being shorter than the duration of at least some of said messages and said time period comprising a plurality of successive time slots;

wherein,

d) at least one of said control nodes is responsive to said access control signal to select a predetermined one of said time slots to begin transmitting one of said messages on said bus if and only if a one of said events to which said control node is responsive has occurred and no other of said nodes has begun transmitting in an earlier said time slots.

2. The network as described in claims 1 wherein said control nodes comprise said central node.

3. The network as described in claim 2 wherein said network is a serial communications network.

4. The network as described in claims 3, wherein said message includes a destination address and another of said control nodes is responsive to said destination address to receive said message.

5. The network as described in claim 4, wherein said another control node returns an acknowledge message to the one of said control nodes transmitting said message.

6. The network as described in claim 2, wherein said message includes a destination address and another of said control nodes is responsive to said destination address to receive said message.

7. The network as described in claim 6, wherein said another control node returns an acknowledge message to the one of said control nodes transmitting said message.

8. The network as described in claim 1, wherein said message includes a destination address and another of said control nodes is responsive to said destination address to receive said message.

9. The network as described in claim 8, wherein said another control node returns an acknowledge message to the one of said control nodes transmitting said message.

10. The network as described in claim 1, wherein the first of said time slots is a priority time slot and each of said control nodes is responsive to priority assignment signals from said central node to set or reset a priority flag so that at most one of said control nodes has its priority flag set;

and wherein further each of said control nodes is responsive to its priority flag being set to select said priority time slot.

11. The network as described in claim 10, further comprising a plurality of second control nodes, wherein said central node communicates with said second control nodes in accordance with a predetermined schedule.

12. A network as described in claim 11, wherein each of said control nodes and said second nodes controls an element of a motion control system.-

13. The network as described in claim 1, further comprising a plurality of second control nodes, wherein said central node communicates with said second control nodes in accordance with a predetermined schedule.

14. The network as described in claim 13, wherein said schedule comprises a cyclic sequence of time intervals, and wherein said central node initiates communications with at least one of said second control nodes during each of said intervals.

15. The network as described in claim 14, wherein said central node transmits synchronization signals on said network to synchronize communication with said second nodes, the period between successive ones of said synchronization signals defining said intervals.

16. The network as described in claim 13, wherein each of said control nodes and said second nodes controls an element of a motion control system.

17. The network as described in claim 1, wherein said access control signal includes a slot control number and each of said control nodes uniquely selects one of said time slots as a distinct function of said slot control number.

18. The network as described in claim 17, wherein said central node changes said slot control number each time one of said control nodes transmits a message.

19. The network as described in claim 18, wherein each of said control nodes stores a node slot register value and said nodes select a time slot as a function of the difference between said node slot register value and said slot control number.

20. The network as described in claim 19, wherein said central node increments said slot control number by one, module the number of said control nodes, each time one of the said control nodes transmits a message.