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Book Overview & Buying
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Table Of Contents
Learning RSLogix 5000 Programming
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Legacy Rockwell PLCs (PLC5 and SLC500) had a dedicated status file (S2), which was continuously updated by the controller with system values. The ControlLogix platform has removed the dedicated status file in order to reduce the controller processing load. In place of the dedicated status file, ControlLogix has provided two self-serve instructions that allow for direct control over the system value access that are neatly organized into class objects. The Get System Value (GSV) instruction will retrieve a system value status from the controller that can update a specified destination tag with that value. The Set System Value (SSV) instruction will update a controller system value status from a specified source tag.

GSV and SSV instructions
The GSV and SSV instructions can be accessed from ladder logic and structured text and are not directly available in function block. Typically, you will see these values scheduled periodically (for example, with a TON...
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