Table 8. LED State/Device Status (Continued)
LED State
Device Status
Blinking, slow (3 blinks/s)
Ethernet activity. Connected at 10 Mbit/s.
Off
No Ethernet connection
Internal Ethernet Switch
The FieldDAQ device features a full hardware-accelerated internal Ethernet switch for greater
performance, wiring flexibility, and compatibility over standard Ethernet ports. The Ethernet
switch exposes two Ethernet ports to the user. Either port can be used to connect the device to
the network. The two ports can be used to connect multiple devices in a daisy-chain topology.
The switch also supports the Rapid Spanning Tree Protocol (RSTP) algorithm, enabling ring
topologies. Refer to
Topology Options
for more details.
IEEE 802.1AS-2011 Precision Time Protocol
The internal Ethernet switch is an 802.1AS time-aware bridge, compatible with the
IEEE 802.1AS-2011 Precision Time Protocol. It can synchronize local measurement signals to
other devices across an 802.1AS subnet. It can also serve as a bridge, synchronizing 802.1AS
devices that are attached to each of the two ports. Refer to
Synchronization across a Network
for more details.
Note
FieldDAQ devices use the IEEE 802.1AS protocol over the network to
synchronize. The IEEE 802.1AS protocol is an IEEE 1588 profile, but is
incompatible with other IEEE 1588 profiles. These FieldDAQ devices cannot
synchronize over the network with devices that use protocols or IEEE 1588 profiles
other than IEEE 802.1AS.
IEEE 802.1Q-2014 Rapid Spanning Tree Protocol (RSTP)
It is possible to create loops in a network using the FieldDAQ device. To prevent these loops
from disrupting the network, the FieldDAQ device implements the IEEE 802.1Q-2014 Rapid
Spanning Tree Protocol (RSTP). Using this protocol, each FieldDAQ device is able to find the
shortest path for incoming packets to reach the rest of the network. When multiple paths exist,
this adds a form of redundancy. If a link fails, the protocol automatically switches to use the
redundant link. This process can take several seconds in some cases.
To gain these benefits on external switches connected to the FieldDAQ device, 802.1w
(RSTP) must be enabled. All external switches must be configured to allow the FieldDAQ
device to transmit 802.1w packets, known as Bridge Protocol Data Units (BPDU). If any
switch has a feature—such as “BPDU guard”—enabled, the port connected to the FieldDAQ
device is disabled and communication is lost. Refer to the documentation for your external
switch for information about enabling RSTP and disabling BPDU guards on the switch.
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FD-11613 User Guide