Method for emulating programmable logic controller by exchanging information between debug program which emulates I/O devices and ladder logic program
First Claim
1. A method in a computer-based development system for emulating a programmable logic controller for debugging a first ladder logic program wherein a second ladder logic program modeled after a particular machine function is provided as a debug program, the method comprising the steps of:
- (a) executing the first ladder logic program and the debug program in the computer-based development system;
(b) scanning one or more rungs in the debug system to generate inputs for driving the first ladder logic program wherein the inputs emulate signals from I/O devices, and storing the inputs as values in an input image data table file for the first ladder logic program;
(c) scanning one or more rungs of the first ladder logic program to generate outputs for driving the debug program wherein the outputs emulate signals to I/O devices and storing said outputs as values in an output image data table file for the first ladder logic program;
(d) comparing, in the debug program, the outputs to a selected response by examining the values in the output image data table file for the first ladder logic program; and
(e) scanning one or more rungs in the debug program to generate additional inputs for driving the first ladder logic program according to the results of the comparing step (d) wherein the additional inputs emulate signals from I/O devices and storing the additional inputs as values in the input image data table file for the first ladder logic program.
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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.
65 Citations
7 Claims
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1. A method in a computer-based development system for emulating a programmable logic controller for debugging a first ladder logic program wherein a second ladder logic program modeled after a particular machine function is provided as a debug program, the method comprising the steps of:
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(a) executing the first ladder logic program and the debug program in the computer-based development system; (b) scanning one or more rungs in the debug system to generate inputs for driving the first ladder logic program wherein the inputs emulate signals from I/O devices, and storing the inputs as values in an input image data table file for the first ladder logic program; (c) scanning one or more rungs of the first ladder logic program to generate outputs for driving the debug program wherein the outputs emulate signals to I/O devices and storing said outputs as values in an output image data table file for the first ladder logic program; (d) comparing, in the debug program, the outputs to a selected response by examining the values in the output image data table file for the first ladder logic program; and (e) scanning one or more rungs in the debug program to generate additional inputs for driving the first ladder logic program according to the results of the comparing step (d) wherein the additional inputs emulate signals from I/O devices and storing the additional inputs as values in the input image data table file for the first ladder logic program. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification