Freezing/clearing counters
- Last UpdatedNov 18, 2022
- 2 minute read
- PI System
- PI Interface for DNP3 3.3.1.38
- Interfaces
This version of the interface provides a means of freezing or freezing/clearing DNP3 Binary Counters (Object 20). The user can use either an output point to freeze counters on demand or an input point to freeze counters as determined by the rate defined by a scan class. When using an output point, the output value of the point specifies they type of freeze request sent to the DNP3 compliant device. Freezing and/or clearing counters using a specified scan rate can be accomplished using input PI points. The input point monitors the return status of the freeze request sent to the device. These PI Points require special attention when being defined and use the Location2 and userint1 to specify the object index to freeze. Refer to the PI Point configuration section of this manual for details relating to configuring points of this type.
The following table shows the meaning of an output value as it relates to a specific freeze request.
|
Output Value |
Meaning |
|---|---|
|
0 |
This function code, Immediate Freeze, is used to copy the specified data objects to a freeze buffer. Upon reception of the message, the Outstation should copy the current values of the specified data objects to their appropriate freeze buffers. The objects which were frozen can be requested (in another request) by asking for frozen objects. |
|
1 |
This function code, Immediate Freeze No Ack., works identically to the previous function code (Immediate Freeze) except that no Outstation response is needed. Typically, this function code is used to perform a global freeze on all Outstations belonging to the master. In this case, the SEND-NO REPLY services of the Data Link Layer may have to be used in certain environments. |
|
2 |
This function code, Freeze and Clear, is used to copy the specified data to a freeze buffer like the immediate freeze function code but then the Outstation clears to 0 the specified data objects. Typically, this function code is used to freeze counters or accumulators and then reset them to 0. |
|
3 |
This function code, Freeze and Clear No Ack., works identically to the previous function code (Freeze and Clear) except that no Outstation response is needed. Typically, this function code is used to perform a global freeze and clear on all Outstations belonging to the master. |