Addressing for a multipoint communication system for patient monitoring

• US 4,638,313 A
• Filed: 11/08/1984
• Issued: 01/20/1987
• Est. Priority Date: 11/08/1984
• Status: Expired due to Term

• Current Assignee: Spacelabs Medical Incorporated (OSI Systems Incorporated)
• Original Assignee: Spacelabs, Inc. (OSI Systems Incorporated)
• Inventors: Sherwood, Glen R. Jr., Moon, James B., Moyle, Gordon A.
• Primary Examiner(s): Weldon, Ulysses
• Application Number:
  US06/669,289
• Time in Patent Office: 803 Days
• Field of Search: 370/86, 370/90, 370/96, 370/85, 370/93, 370/92, 370/79, 370/89, 340/825.05, 340/825.07, 340/825.08, 340/825.5, 340/825.51, 340/825.06, 340/825.52, 340/825.53
• US Class Current: 340/9.16
• CPC Class Codes: G06F 12/0661 and decentralised selection
• CPC Class Codes: H04L 61/5038 for local use, e.g. in LAN or USB networks, or in a controller area network [CAN]
• CPC Class Codes: H04L 61/5046 Resolving address allocation conflicts; Testing of addresses testing when self-assigning an address H04L61/5092
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A method for dynamically assigning addresses to new modules as they are coupled to a communication system with a synchronous data link control (SDLC) bus is described. These modules communicate with a display unit via the SDLC bus. The SDLC bus is controlled by a primary station in the display unit, with all modules acting as secondary stations. The primary station periodically broadcasts a time-tag to all modules at a thirty-two hertz rate. At power up, each module obtains a number, module 16, derived from the lower four bits of its unique twenty-four bit serial number. The module uses this number as a count of the number of time-tags which must occur before the module responds to the primary with an address request. If there are no collisions with other modules, the primary sends the module a packet which assigns the module the next available address. In the event of a collision (i.e., two or more modules request an address at the same time), the primary SDLC controller detects a CRC error and ignores the SDLC frame. The modules will each time-out and obtain a new number, modulo 16, derived from the next significant four bits of the module serial number. This process continues until the module obtains an address.

Claims

1. A method of synchronizing to a multipoint communication system wherein a primary station repeatedly polls a plurality of secondary stations coupled together over a serial data bus comprising the steps of:

dynamically assigning an address to a new secondary station upon coupling to said system, said step of dynamically assigning further comprising the steps of;

broadcasting time-tags to all of said secondary stations simultaneously during an address initialization phase at the beginning of each poll interval;

automatically determining a first time-tag count number of poll intervals for each of said new secondary stations upon coupling to said system;

waiting said time-tag count number of poll intervals to choose a poll interval for requesting an address assignment from said primary station during said address initialization phase of said chosen poll interval;

requesting said address assignment, and

assigning an address to said secondary station in response to said request.

2. The method of claim 1 wherein said method further comprises the steps of:

automatically determining second and subsequent time-tag count numbers as required when two or more secondary stations request address assignments during a chosen poll interval which is the same for the two or more secondary stations.

3. The method of claim 2 wherein said method further comprises the steps of:

preassigning to each secondary station a unique multibit serial number;

choosing a first predetermined subset of said multibit serial number as the basis of said first count number; and

choosing a second predetermined subset of said multibit serial number as the basis for a second count number in the event of a simultaneous address request by two or more secondary stations, and so on until each new secondary station receives an address assignment.

4. The method of claim 3 wherein each of said predetermined subsets of said multibit serial number comprises said count number associated with each said predetermined subsets.

5. The method of claim 2 wherein said method further comprises the steps of:

preassigning to each secondary station a unique multibit serial number; and

using said serial number as the seed of a random number generator to generate a series of random numbers for use as the basis for said count numbers.

6. The method of claim 1 wherein each of said new secondary stations assumes a predetermined address until a unique address is assigned by said primary station.