Programmable controller with multiple priority level task processing

• US 5,193,189 A
• Filed: 12/09/1991
• Issued: 03/09/1993
• Est. Priority Date: 10/07/1987
• Status: Expired due to Term

• Current Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Original Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Inventors: Kalan, Michael D., Peterson, Alden L. II, Preis, Peter N., Flood, Mark A.
• Primary Examiner(s): Fleming, Michael R.
• Assistant Examiner(s): Ray, Gopal C.
• Application Number:
  US07/809,085
• Time in Patent Office: 456 Days
• Field of Search: 395/325, 395/775, 395/650, 395/700, 395/275, 395/725, 364/131, 364/140, 364/147, 364/200 MS File, 364/900 MS File, 364/DIG. 1 M S File, 364/DIG. 2 MS File, 318/569, 340/825.22, 370/77
• US Class Current: 718/103
• CPC Class Codes: G05B 19/052 Linking several PLC's
• CPC Class Codes: G05B 2219/15081 Period length ratio between application and communication task is settable

Abstract

A programmable controller for operating a machine to perform programmed functions allows the user to allocate the amount of processing time to be devoted to a machine control program and to user defined background tasks. The allocation is defined by an entry stored in one of several locations in a data table. Each occurrence of a timed interrupt steps the operating system through the data table. When the operating system accesses the location at which the entry is stored, the machine control program is assigned as lower execution priority than any background tasks to be executed. When the last storage location of the data table is accessed, the user control program is restored to a higher execution priority than the background tasks before initiating another stepping sequence through the data table.

Claims

1. A programmable controller, for operating a machine to perform programmed functions, which comprises:

a first means for storing a plurality of user defined programs, including a machine control program;

a processing means, coupled to said first means for storing, for executing the user defined programs;

a second means for storing a first data table containing pointers to different types of programs in a priority order in which the different types are to be executed by said processing means, two types of programs being the machine control program and the other user defined programs, said processing means being coupled to said second means for storing for the placement of pointers therein to designate programs for execution;

designating means for a user to define an amount of program execution time of said processing means to be devoted to the execution of other user defined programs than the machine control program;

means, coupled to said second means for storing, for controlling amounts of time that the machine control program and other user defined programs are executed by said processing means on a time-slice basis by reversing the relative priority order of the machine control program and the other user to defined programs in the first data table in response to the amount of program execution time defined by said designating means to which is connected to said means for controlling; and

means for coupling input and output devices on the machine to the processor means.

2. The programmable controller as recited in claim 1 wherein said means for controlling includes means for interrupting the execution of the machine control program to permit the execution of other user defined programs.

3. The programmable controller as recited in claim 1 wherein said means for controlling includes means for halting the execution of the other user defined programs and returning said processing means to the execution of the machine control program after the other user defined programs have been executing for a predetermined interval of time.

4. The programmable controller as recited in claim 3 wherein said means for controlling includes means for suspending the execution of a user defined program when such execution is not completed at the expiration of the predetermined interval, and then causing the execution of the suspended user defined program to resume upon a subsequent interruption of the execution of the machine control program.

5. The programmable controller as recited in claim 1 further comprising:

a third means for storing coupled to said processing means and having a series of storage sections, each section containing parameters received from said processor means which are used during the execution of a given user defined program, some of the sections also containing a pointer to another section which contains parameters for another user defined program;

wherein the first data table contains a pointer to one of the sections of said third means for storing contains parameters for a program to be executed.

6. The programmable controller as recited in claim 1 wherein said program execution control means includes:

a fourth means, responsive to said processing means, for storing a second data table having a plurality of locations for storing an indicium of a program to be executed;

means for periodically and sequentially accessing each location in the second data table and causing said processing means to execute any program indicated therein; and

means for loading into a location in the second data table an indicium of a program routine which reverses the priority order of the machine control program and the other user defined programs in the first data table, the location in the second data table in which the indicium is loaded is determined by the selection of the amount of execution time by the user.

7. A programmable controller for operating a machine to carry out a plurality of programmed functions, comprising:

a memory means for storing a user defined machine control program, a user defined background task program, a first data table for storing pointers to different programs in a priority order in which the different programs will be executed, and a second data table having a plurality of storage locations for storing a pointer to an operating system routine, said memory means storing an operating system program for reversing the order in the first data table of the pointers to a machine control program and a background task program;

a processing means for executing the user control program and the background task program thereby enabling the programmable controller to perform specific programmed functions, said processing means coupled to said means for storing to exchange program instructions and data therebetween;

means for a user of the programmable controller to specify relative amounts of time that the processing means is to devote to executing the machine control program and the background task program, and loading a pointer to the operating system program in a specific one of the plurality of storage locations in the second data table which corresponds to a relative amount of time specified by the user; and

means for sequentially accessing the storage locations of the second data table and causing said processing means to execute a program designated by a pointer stored in such storage locations, and being functionally coupled to said processing means and to said memory means.