Method and apparatus for symbolic ladder logic programming with automatic attachment of addresses

• US 5,349,518 A
• Filed: 06/30/1989
• Issued: 09/20/1994
• Est. Priority Date: 06/30/1989
• Status: Expired due to Term

• Current Assignee: ICOM Incorporated
• Original Assignee: ICOM Incorporated
• Inventors: Zifferer, Scott C., Menter, Joseph J. Jr.
• Primary Examiner(s): Kulik, Paul V.
• Application Number:
  US07/374,487
• Time in Patent Office: 1,908 Days
• Field of Search: 364/200 MS File, 364/900 MS File, 364/200, 364/900, 364/188, 364/189, 364/147, 364/192, 364/191, 364/193, 371/19, 395/575, 395/700, 395/800, 395/161
• US Class Current: 700/87
• CPC Class Codes: G05B 19/05 Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
• CPC Class Codes: G05B 2219/13057 Automatic search for unused, available address; assign to symbol
• CPC Class Codes: G05B 2219/13067 Use of variables, symbols in instructions, to indicate mechanisms, interfaces
• CPC Class Codes: G05B 2219/13114 Use of relative addresses for program
• CPC Class Codes: G05B 2219/13125 Use of virtual, logical connections
• CPC Class Codes: Y10S 715/967 Visual or iconic programming

Abstract

The present invention discloses a method of identifying elements in a plurality of data table files of a programmable logic controller using symbols to represent the addresses thereof. This, and other techniques, provide means for managing and economizing the allocation of memory. The software package tracks which of the elements are represented by symbols and which of the elements are available. Symbols can be attached to element addresses by the user displaying a list of previously defined symbols and selecting a symbol from the list. Symbols can be attached to element addresses by the user selecting a particular Data Table file and simply requesting the next available element address from the file. Symbols can also be automatically attached to elements in new Data Table files. The user specifies the file type for the new Data Table file and the software package creates the new file. At the same time, the software package will automatically attach the symbol to the address of the first element in the new created file. The user has the option of manually attaching symbols to elements in the Data Table files. The user selects a Data Table file and the software package displays the contents of the file on the screen. The user positions the cursor on the desired element and the software package attaches the symbol to the address of the element.

Claims

1. A method of providing symbol help in a program editor executed by a computer, the program editor being used by an operator for the displaying and editing of a ladder logic program on a monitor attached to the computer, wherein the ladder logic program is comprised of instructions operating on elements of data tables, the method comprising:

(a) maintaining a symbol assignment record in the computer, wherein the symbol assignment record identifies a correspondence between symbols and elements of the data tables, wherein each element is assigned to a specific symbol and each symbol represents a specific element, so that instructions in the ladder logic program reference an element using a symbol representing the element;

(b) displaying a list of symbols obtained from the symbol assignment record on the monitor while the program is being edited, receiving a command from the operator selecting a symbol from the displayed list of symbols, and modifying an operator-identified instruction in the program so that it references the selected symbol; and

(c) wherein the displaying step (b) further comprises receiving commands from the operator specifying a portion of a desired symbol, and displaying in the list of symbols only those symbols from the symbol assignment record which match the portion of the desired symbol.

2. The method of claim 1, further comprising receiving commands from the operator identifying additional portions of the desired symbol, and displaying in the list of symbols only those symbols from the symbol assignment record which match the additional portions of the desired symbol.

3. An apparatus for providing symbol help in a program editor executed by a computer, the program editor being used by an operator for the displaying and editing of a ladder logic program on a monitor attached to the computer, wherein the ladder logic program is comprised of instructions operating on elements of data tables, the apparatus comprising:

(a) means for maintaining a symbol assignment record in the computer, wherein the symbol assignment record identifies a correspondence between symbols and elements of the data tables, wherein each element is assigned to a specific symbol and each symbol represents a specific element, so that instructions in the ladder logic program reference an element using a symbol representing the element;

(b) means for displaying a list of symbols obtained from the symbol assignment record on the monitor while the program is being edited, receiving a command from the operator selecting a symbol from the displayed list of symbols, and modifying an operator-identified instruction in the program so that it references the selected symbol; and

(c) wherein the means for displaying (b) further comprises means for receiving commands from the operator specifying a portion of a desired symbol, and means for displaying in the list of symbols only those symbols from the symbol assignment record which match the portion of the desired symbol.

4. The apparatus of claim 3, further comprising means for receiving commands from the operator identifying additional portions of the desired symbol, and means for displaying in the list of symbols only those symbols from the symbol assignment record which match the additional portions of the desired symbol.