Eaton’s Crouse-Hinds Business
Cooper Crouse-Hinds Pte Ltd
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Singapore 554911
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Number of devices on live list
Number of active fieldbus devices on the network segment.
The live list is the list of all devices that are properly responding to the Pass Token
(PT) message.
New devices may be added to the fieldbus at any time. The LAS periodically sends
Probe Node (PN) messages to the addresses
not in the Live List. If a device is present
at the address and receives the PN, it immediately returns a Probe Response (PR)
message. If the device answers with a PR, the LAS adds the device to the Live List and
confirms its addition by sending the device a Node Activation message.
A typical segment consists of:
o
Primary host card (LAS, Link Active Scheduler, active Link Master)
o
Redundant host card (secondary Link Master)
o
Field instruments, such as transmitters, valve positioners
o
F809F diagnostic module, if configured to communicate on this segment
(typically segment 8)
o
Potentially a handheld communicator such as Emerson 475.
o
Non-communicating fieldbus tester such as FBT-6 will
not
count/appear as a
device.
Default limit is 0..32 devices. Connecting an handheld fieldbus tester FBT-6 will not
count as a device; however, a communicator such as Emerson 475 will. If connecting a
communicator should not generate an alarm, the upper limit should be increased
by 1.
Once the number of devices is confirmed, low limit can be set to the actual number
of devices if the F809F should generate an alarm to the system, for example if a
device is removed. As however DCS systems detect missing devices themselves, this
alarm would be a duplication. In such case, set the limits to the default 0..32 devices
to avoid an alarm by the F809F.
