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Table 10. 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
IEEE 802.1AS-2011 Precision Time Protocol
The internal Ethernet switch is an IEEE 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 IEEE 802.1AS subnet. It can also serve as a bridge, synchronizing
IEEE 802.1AS devices that are attached to each of the two ports. Refer to
IEEE 802.1Q 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 Rapid
Spanning Tree Protocol (RSTP). Using this protocol, each FieldDAQ device can 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, IEEE 802.1Q
(RSTP) must be enabled. All external switches must be configured to allow the FieldDAQ
device to transmit RSTP 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.
IEEE 1588 Delay Request-Response Default Precision Time
Protocol
The internal Ethernet switch can be configured to act as a 1588 "boundary clock"
implementing the IEEE 1588 delay request-response default PTP profile (sometimes referred
to as "default profile"). When so configured, it can synchronize local measurement signals to
other devices across an IP subnetwork and can serve as a bridge, synchronizing 1588 devices
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FD-11634 User Guide
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