Emerson AMS Trex Device Communicator User Manual page 104

Field Communicator application
September 2021
3.18.5
104
1.800.561.8187
Only one device can communicate at a time. Permission to communicate on the bus is
controlled by a centralized token passed between devices by the LAS. Only the device with
the token can communicate. The LAS maintains a list of all devices that need access to the
bus. This list is called the Device List.
Although the Trex unit can be the LAS, it does not maintain the communication schedule
and should not be thought of as a backup LAS. When the Trex unit is connected to a live
fieldbus segment, it joins the fieldbus segment, but not as the LAS. The Trex unit can view
and edit device parameters, but the LAS controls the segment.
The device acting as the LAS is labeled on the Device List screen.
Fieldbus Device List
The Device List displays all devices that the Trex unit has detected. Each device is listed by
its tag and address. The last four numbers of the Trex serial number are displayed to
identify the Trex unit. The Device List also identifies the host on the fieldbus segment and
which device is the LAS.
Tap a device listed on the screen to connect to it. If a device is not listed, tap the My
Device Not Found button. This option expands the following settings:
• Polling addresses - By default, the Trex unit polls addresses 0-48 and 232-255. This
range is then expanded to include all valid fieldbus addresses.
• Slot time - The slot time is increased to enable the Trex unit to find older FOUNDATION
fieldbus devices on the fieldbus segment.
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