Process and device for high speed polling

• US 4,942,572 A
• Filed: 06/26/1989
• Issued: 07/17/1990
• Est. Priority Date: 12/30/1986
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Picard, Jean-Louis
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Marcelo, Melvin
• Application Number:
  US07/372,146
• Time in Patent Office: 386 Days
• Field of Search: 370/84, 370/85.2, 370/85.8, 370/95.2, 340/825.08
• US Class Current: 370/449
• CPC Class Codes: G06F 13/22 using successive scanning, e.g. polling G06F13/24 takes precedence
• CPC Class Codes: H04L 12/4013 Management of data rate on the bus systems modifying transmission characteristics according to link quality H04L1/0001
• CPC Class Codes: H04L 12/403 with centralised control, e.g. polling
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]

Abstract

A process is disclosed for efficiently polling low rate data terminals attached to communicate with a central station via a high speed channel. The process is based on the use of a dual rate polling mechanism involving first polling by using a high rate pseudo random sequence; monitoring the messages received back from the terminals; checking said messages for validity, and upon detecting an invalid message possibly indicating collision between terminal messages, then switching back into the first generated sequence at a lower conventional rate.

Claims

1. A system for polling from a microprocessor controlled Communication Controller, N digital terminals made to communicate with said Controller via a high speed channel, said system including at the Controller site:

means sensitive to an order from said microprocessor for generating and broadcasting a specific pattern announcing subsequent polling operations;

a pseudo random generator sensitive to a subsequent order from said microprocessor for generating and broadcasting a first high rate equal to the bit rate, a random polling sequence of station addresses in which sequential station addresses are separated in time at the broadcasting rate by z bits of other station addresses where z is a whole number greater than or equal to 80.

sensing means within said microprocessor controlled Communication Controller for monitoring the message received back from the terminals;

inhibit means connected to said sensing means for subsequently broadcasting an inhibit message for inhibiting further message sending from the terminals upon a received message being detected by said sensing means;

validity checking means sensitive to said sensing means for checking the validity of said received message; and

means sensitive to an invalidity being reported by said validity checking means for switching said polling to a second low rate polling means.

2. A polling system according to claim 1 wherein said second low rate polling means includes means for repeating at a lower rate the polling of a limited number of terminal addresses polled by the pseudo random generator just prior to the occurrence of an invalid check.

3. A polling process for polling from a central station N terminals made to communicate with said central station using digital frames including validity checking means, said process including steps of:

generating and transmitting from said central station, a first polling sequence of station addresses at a first high rate equal to the bit rate and having sequential station addresses separated in transmitting time from one another by at least z bits of other station addresses, where z is a whole number greater than or equal to 80;

monitoring at said central station the data received back from said terminals being polled;

checking for validity the received data at said central station; and

, upon detecting invalid data received,

repeating at said central station and transmitting at a second lower rate a polling sequence addressing a limited number of the terminals just polled prior to the invalid check;

and said method being characterized in that said first polling rate sequence is pseudo-randomly generated.