FieldPoint Watchdog Timer

FieldPoint network modules can detect unexpected periods of network inactivity and respond to them in a user-defined way. The network watchdog feature enables you to guard your system against failures in the network connection, cables, or host computer, and to put the channel outputs in a user-defined state (the watchdog state) if such failures do occur. If you are running embedded applications on FieldPoint RT modules ([c]FP-20xx) that do not require communication with a host computer or clients, the network watchdog may not be appropriate. The [c]FP-20xx network modules also support a hardware watchdog that you can set up in LabVIEW RT for use with embedded applications.

Enabling and Configuring the Network Watchdog

Network watchdog output values can be different from power-up output values. For example, you may want to turn on an output value when you power up, but turn it off if network communication is lost.

The network watchdog for the bank is disabled by default. Follow these steps to enable it:

1. In the FieldPoint software, right-click an output module and select Edit this device.
2. Select Enable or Enable on Use for the current watchdog configuration.
3. Click Channel Configuration, then configure these settings:
· Enable/disable the watchdog for each channel.
· Enter a watchdog data value for each channel.
4. Click OK.
5. In the left pane, right-click the network module, select Edit this device, and configure these settings:
· Make sure the factory configuration checkbox is unchecked.
· Enable network watchdog for the bank.
· Enter a network watchdog timer value for the bank, a value that specifies the maximum allowable period of lost communication with hosts or clients over the network.
6. Click OK.
7. Select File»Save.

Refer to KB - 1YLIO1M6 to see how to use the power-up and watchdog settings of the FieldPoint modules together.

Hardware Watchdog (FP-20xx Only)

In addition to the network watchdog, the FP-20xx network modules support the hardware watchdog available in LabVIEW RT. The hardware watchdog provides a programmatic way of verifying that the FP-20xx is responding within a given time period. For example, it can be configured to reset the FP-20xx or to generate an occurrence in LabVIEW if the module stops responding because of a problem in the program. The hardware watchdog VIs can be found on the FieldPoint »FieldPoint RT »FieldPoint Watchdog palette of LabVIEW. Include these VIs as subVIs in your FieldPoint executable if you want to use the hardware watchdog. For examples that show how to use the hardware watchdog, refer to the RT Watchdog (PXI).llb file installed under \\examples\Real-Time.

How the Network Watchdog Works

The network watchdog works differently on serial network modules than it does on Ethernet network modules. In either case, the watchdog does not start monitoring network activity until the network module is polled (in the case of serial connections) or a FieldPoint server subscribes to a data item (in the case of Ethernet connections).

FieldPoint Serial Network Modules
FieldPoint serial network modules send data only when polled by the host computer. Each time the host computer polls the module, the watchdog timer is reset. If the watchdog timeout period expires before the network module is polled, the network module reverts to the user-defined watchdog settings.

FieldPoint Ethernet Network Modules
When you start the FieldPoint server (such as running FP Open.vi, opening FieldPoint Explorer, or accessing the OPC server), the server requests a subscription from the network module for each Ethernet item in its .iak file. The network module maintains a count of all the subscriptions granted to a FieldPoint server(s). The set of subscriptions also has a heartbeat associated with it, a small amount of data is transmitted back and forth periodically between the subscribing FieldPoint server and the network module. This heartbeat is one of the reasons you see periodic network activity on an Ethernet network module even when the data is not changing. The watchdog timer is then reset each time the network module receives the heartbeat. If the watchdog timeout period expires before the network module receives the heartbeat from a FieldPoint server, the watchdog deactivates the subscriptions for that server. If the subscription count falls to '0', the network module reverts to the user-defined watchdog settings.

When you close a FieldPoint server, you deactivate the subscriptions for that server. If that server was the only one subscribing to data items from the network module, the subscription count falls to '0' and the network module reverts immediately to the user-defined watchdog settings.

Refer to KB - 17F9KN8U to see some FieldPoint watchdog timer questions.

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