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FS-8704-09 SNMP Driver Manual Page 18 of 39
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Appendix A.2. Sending SNMP TRAPS using the SNMP Server/Agent
There are two ways to send traps using the driver
• A rule based appoach – COV (Change of Value): Driver watches a data point. If the data changes and meets the condition of some rule then
the trap is generated.
• Non-rule – Driver sends the trap uncondionally based on a time interval or whenever the source data point is udpated (even if there is no
change.)
Change of Value (COV) Traps
Rules determine when to send an SNMP Trap. These rules are configured in Server Side Map Descriptors, and are applied to the data whenever
it changes. Traps are sent on a Change of State (COS) of the relevant Data Array value, as determined by the following configurable criteria:
COS_Hi_Alm High Alarm threshold, applies to numerical values
COS_Hi_Warning
High Warning threshold, applies to numerical values
COS_Lo_Warning
Low Warning threshold, applies to numerical values
COS_Lo_Alm Low Alarm threshold, applies to numerical values
COS_Deadband Deadband value which must be crossed for Alarm or Warning states to toggle (prevents chatter)
COS_Normal Normal value for a digital point (1 or 0) – when the value changes to or from Normal, a Trap is sent. For an analog point set
the 'COS_Normal' parameter = 'COS_Server_Event' and then specify the dead band. Each time the the analog value
changes by at the deadband or more (absolute change) then a trap will be sent
Each Trap Map Descriptor must specify the destination of the Trap by configuring a Remote_Client_Node_Descriptor, as shown in the example
below. The OID to which the data value is to be bound in the Trap message is specified in the Map Descriptor.
First, the Trap destination Node is set up as follows:
Remote_Client_Node_Descriptors
Node_Name,
Node_ID,
Protocol, Adapter,
IP_Address
NM_1, 1, SNMP, N1, 192.168.1.174
The Trap Map Descriptors are then configured as below, using the desired COS rule parameters:
// Server Side Map Descriptors
Map_Descriptors
Map_Descriptor_Name, Data_Array_Name, Data_Array_Offset, Function, Node_Name, SNMP_OID, COS_Hi_Alm, COS_Lo_Alm, COS_Deadband
PSU_Voltage_Alarm, DA_AI3, 0, SNMP_TRAP, NM_1, 1.3.6.1.4.1.6347.1.1.0.0, 10.5, 7.3, 0.2