Propagation of a signal along wires may vary according to whether a field device exists and whether a tag number was assigned to an I/O channel. If the tag number was assigned to an I/O device the cables connected to the I/O terminals are also considered during the signal propagation. The method of propagating sequence numbers (within a level) used by Smart Instrumentation depends on whether a field device is associated with that tag number, and whether the wiring routing is complete (there is a signal continuity between the field device and the I/O channel).
Diagram key:
A — Field device without a channel.
B — Field device and Control System channel assigned without cables connected to the Control System channel.
C — Field device and Control System channel assigned with cables. Wiring routing is not completed.
D — Field device and Control System channel assigned. Wiring routing is completed.
E — Control System channel assigned without a field device.