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.

Abstract: The present invention discloses a software package for developing ladder logic programs for Programmable Logic Controllers (PLCs). The present invention provides a method of troubleshooting ladder logic programs for a programmable logic controller. The ladder logic program is debugged using an emulator executing on a computer. The emulator executes a second ladder logic program. The second ladder logic program generates the inputs that drive the ladder logic program being debugged. The second ladder logic program is comprised of output instructions that drive input instructions in ladder logic program being debugged. Thus, the emulator simulates the operation of the programmable logic controller.

Abstract: The present invention is a method that provides productivity aids for developing, debugging, and troubleshooting ladder logic programs used in Programmable Logic Controllers (PLCs). The present invention discloses methods for searching ladder logic programs of programmable logic controllers for instructions, addresses, and symbols. The user can select an address or symbol in the ladder logic program and display on a computer a cross-reference list for the selected address or symbol. The cross-reference list shows all ladder logic instructions, and their locations in the ladder logic program, that use the selected address or symbol. An instruction location can be selected from the cross-reference list and the corresponding point in the ladder logic program will be displayed on the computer.

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.

Abstract: The present invention discloses a method of securing access to different functions in a ladder logic programming and monitoring system. Access to various functions of the software package can be controlled using the security system of the software package. When shipped, the security system is disabled. The security system can be activated after a master password is entered for the first time. The person configuring the security system, i.e., the system supervisor, sets up the access rights of all other users. Thereafter, to gain access to the software package, the user must enter his name and unique password. The user can access only those functions assigned to his name and password.

Abstract: The present invention provides productivity aids for ladder logic programs for Programmable Logic Controllers (PLCs). The present invention discloses a software package embodying a method of creating custom screens for displaying the values and status of bits and words in a PLC as a ladder logic program executing therein is monitored. Any combination of bits and words can be displayed by the custom screens. This Custom Data Monitor function is designed to simplify troubleshooting by giving the user the tools to develop screens that act as windows into user-selected Data Table locations in the PLC.