A network’s Monitor slot holds configuration for the “ping mechanism” used by the driver network. In the network’s property sheet, expand the Monitor slot to see configuration (Figure 11).
Monitor provides verification of the general health of the network, plus the network’s “pingables” (typically, devices) by ensuring that each device is minimally “pinged” at some repeating interval.
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If a device responds to the monitor ping, device status is typically “ok,” and normal communications routines to it (proxy-point polling, plus reads of device schedules, trends, etc. if supported by the driver) proceeds normally. Typically, this applies even if the device returns an error response to the ping, because this indicates that the device is “alive.”
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If a device does not respond to the monitor ping, it is marked with a down status—this causes normal communications routines to that device to be suspended. Upon the next successful monitor ping to that device, device status typically returns to “ok” and normal communications routines resume.
Whenever successful communications occur to a device, that device component’s Health property is updated with the current time. The network ping Monitor will only “ping” the device if the time of last health
verification is older than the ping frequency. Therefore, in normal operation with most drivers, the proxy point
polling mechanism actually alleviates the need for the monitor ping, providing that the ping frequency is long enough. Also,
in most drivers if a point poll request receives no response (not even a “null”) from a device, a “ping fail” condition is
immediately noted, without waiting for the monitor ping interval.
The following sections provide more Monitor details:
The monitor ping properties are as follows:
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Ping Enabled
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If true, (default) a ping occurs for each device under the network, as needed.
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While set to false, device status pings do not occur. Moreover, device statuses cannot change from what existed when this property was last true.
It is recommended you leave Ping Enabled as true in almost all cases.
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Ping Frequency
Specifies the interval between periodic pings of all devices. Typical default value is every 5 minutes (05m 00s), you can adjust differently if needed.
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Alarm On Failure
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If true (default), an alarm is recorded in the station’s AlarmHistory upon each ping-detected device event (“down” or subsequent “up”).
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If false, device “down” and “up” events are not recorded in the station’s AlarmHistory.
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Startup Alarm Delay
Specifies the period a station must wait after restarting before device “down” or “up” alarms are generated. Applies only if the Monitor’s property Alarm On Failure is true.
The monitor mechanism used by a specific driver may have unique characteristics.
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For example, in a BacnetNetwork, any monitor ping is directed to the device’s BACnet “Device Object,” and in particular, to its “System_Status” property. In this unique case, a received response of “non-operational” is evaluated the same as getting no response at all!
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Or, in any Modbus network, when a monitor ping message is sent, it is directed to the device’s “Ping Address,” which is configured by several properties in the ModbusDevice object.
Other drivers may have specific considerations for the Monitor ping mechanism. For more information, refer to the “Device Monitor Notes” section within any NiagaraAX driver document.