Communication network polling technique

• US 4,829,297 A
• Filed: 05/08/1987
• Issued: 05/09/1989
• Est. Priority Date: 05/08/1987
• Status: Expired due to Term

• Current Assignee: Allen-Bradley Company Milwaukee WI
• Original Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Inventors: Ilg, Gregory R. S., Jones, Lester A., Flood, Mark A.
• Primary Examiner(s): YUSKO, DONALD
• Application Number:
  US07/047,313
• Time in Patent Office: 732 Days
• Field of Search: 340/825.08, 340/825.5, 340/825.07, 340/825.02, 340/825.03, 340/825.51, 370/112, 370/90, 370/96, 178/2 R
• US Class Current: 370/449
• CPC Class Codes: G06F 13/225 with priority control
• 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

Abstract

In a communication network wherein a master station periodically polls a number of remote stations to determine whether or not each remote station has data to transmit to the master, each of the remote stations is assigned to one two groups. One of the groups is designated as priority stations which commonly have very urgent data for the master station. The group of non-priority stations is sequentially polled for messages to be sent to the master station. The polling of the group of non-priority stations is periodically interrupted so that the master station may poll each of the stations in the priority group to determine if they have messages to send. Upon the completion of the polling of the priority stations, the polling of the non-priority stations is resumed. Periodically a time period occurs for inactive stations to join one of the two groups of stations on the network. This method permits stations that typically have high priority data, to transmit that information more frequently than would be possible if only one polling group of stations existed.

Claims

1. A method for polling stations on a communications network comprising the steps of:

sequentially polling each station in a first group of active stations for messages to be sent on the network by sending a command to each such station;

periodically interrupting the polling of the first group of active stations to poll at least one station in a second group of stations for messages to be sent on the network by sending a command to each such station, whereby the stations in one group are polled more frequently than the stations in the other group; and

resuming the sequential polling of the first group of stations upon the completion of polling of at least one station in the second group.

2. The method as recited in claim 1 wherein the amount of data that a station may send each time that it is polled is limited to a fixed amount;

and further comprising, when a given station is found with a message to send, continually polling only that given station until the entire message has been sent.

3. The method as recited in claim 2 wherein said step periodically interrupting the polling of the first group of stations includes inhibiting the interrupting while a station is sending a message.

4. The method as in claim 1 further comprising the step of occasionally polling a station that is not a member of either group to determine if it desires to join one of the groups of stations.

5. A method as in claim 1 wherein the steps of polling the first group or the second group of stations, both include the step of deleting a station from the respective group which does not respond to being polled.

6. The method as in claim 1 wherein the steps of sequentially polling the first group of stations is commenced at periodic intervals.

7. The method as in claim 1 wherein all of the stations in the second group are sequentially polled every time the polling of the first group of stations is interrupted.

8. In a communication network having a master station capable of accessing X number of station addresses, a method of polling stations on the network comprising the steps of:

(a) defining a subset of Y station addresses such that Y is less than X;

(b) assigning each station on the network a unique address selected from the subset of Y station addresses;

(c) sequentially polling a first group of active station addresses within the subset for messages to be sent on the network;

(d) interrupting the polling of the first group of station addresses to poll at least one station address in a second group of active station addresses within the subset for messages to be sent on the network, said interrupting occurring at a given interval from when the second group of station addresses was last polled; and

(e) then continuing the sequential polling of the first group of station addresses.

9. The method as in claim 8 further including allowing the master station to transmit messages after the completion of polling each station within the first group.

10. The method as in claim 8 further including the step of occasionally polling each of the station addresses within the subset that are not in either the first or second group to determine if the address is assigned to a station that seeks to join one of the two groups of station addresses.

11. The method as recited in claim 8 wherein in step (e) the sequential polling of the first group of station addresses continues from the point where the polling was previously interrupted.

12. A method for polling stations on a communication network comprising the steps of:

sequentially polling each station in a first group of active stations for messages to be sent on the network by sending a command to each such station;

occasionally interrupting the polling of the first group of stations to poll at least one station in a second group of active stations for messages to be sent on the network by sending a command to each such station;

;

and

resuming the sequential polling of the first group of stations upon the completion of polling of at least one station in the second group, whereby the stations in one group are polled more frequently than the stations in the other group.

13. The method as recited in claim 12 wherein when a given station is found with a message to send, continually polling only that given station until the entire message has been sent.

14. The method as recited in claim 12 wherein the sequential polling of the first group of station addresses resumes from the point where the polling was previously interrupted.

15. The method as in claim 12 further including the step of occasionally polling station addresses that are not in either the first or second group to determine if the address is assigned to a station that seeks to join one of the two groups of station addresses.