Signal propagation is a method used in Smart Instrumentation to associate wires with instruments. A signal or a tag signal is a software identifier that is associated with a particular instrument tag, and is generated in a device panel or locally within other types of panels. A tag signal can also be created as a result of I/O assignment.
When you connect or disconnect a cable, cable set, or wire, Smart Instrumentation automatically updates the wire tags and the signals that are carried by the wires. Tag signal propagation takes place automatically, with consequent updating of wire names, and signal sequences. Signal sequence values are sequential numbers assigned consistently to all the wires within a given wire group along the signal path of that wire group. Automatic tag signal propagation also takes place after you effect I/O assignment. For details of various tag signal propagation results, see Possible Cases of Signal Propagation.
However, there may be situations in which tag signal propagation does not occur automatically. In this case, Smart Instrumentation offers you two options for semiautomatic propagation of a selected tag signal. You can re-propagate a tag signal or force tag signal propagation. For details, see Force Signal Propagation and Re-Propagate a Tag Signal.
Also, you can effect signal propagation at terminal strip level by manually entering or changing a signal or its level at any point along the wiring path.
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To propagate signals through jumpers you must have selected the Propagate tag signal through jumpers option in the Wiring > Jumpers preferences.
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You can assign a wire group to a jumper manually on the Terminal Connection dialog, if you have not selected the Propagate tag signal through jumpers option.
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Tag signal propagation for a shield takes place automatically without the need to connect that shield to a device panel terminal.
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Tag signal propagation stops if it reaches a point where multiple optional paths exist.
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You can re-propagate or force propagation of tag signals if this is required.
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You can intervene at any point of the wire path and change tag number propagation manually.
You can generate a point-to-point wiring diagram and view the signal path after you finish assigning an instrument tag to a channel in an I/O card. For information about point-to-point diagrams, see Trace a Signal in a Point-to-Point Wiring Diagram.