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Frozen counters

Outstation shall freeze a specific counter value in time. This feature allows the counter's value to be captured and reported without interrupting its ongoing operation. The frozen values can be exchanged between master and outstation in several variations, supported variations are described as below.

Static variation:

  1. 32-bit with flag - It sends the current frozen value in an unsigned 32-bit integer with status (quality flags). Range is from 0 to 4,294,967,295. 

  2. 16-bit with flag - It sends the current frozen value in an unsigned 16-bit integer with status (quality flags). Range is from 0 to +65535. 

  3. 32-bit with flag & time - It sends the current frozen value in an unsigned 32-bit integer with status (quality flags) and time of the event occurrence. Range is from 0 to 4,294,967,295. 

  4. 16-bit with flag & time - It sends the current frozen value in an unsigned 16-bit integer with status (quality flags) and time of the event occurrence. Range is from 0 to +65535. 

  5. 32-bit without flag - It sends the current frozen value in an unsigned 32-bit integer without status (quality flags). Range is from 0 to 4,294,967,295. 

  6. 16-bit without flag - It sends the current frozen value in an unsigned 16-bit integer without status (quality flags). Range is from 0 to +65535. 

Event variation:

  1. 32-bit with flag – frozen counter event is reported to master as signed 32-bit integer with quality (status) flags. Range is from -2147483648 to +2147483647. 

  2. 16-bit with flag – frozen counter event is reported to master as signed 16-bit integer with quality (status) flags. Range is from -32768 to +32767. 

  3. 32-bit with flag and time – frozen counter event is reported to master as signed 32-bit integer with quality (status) flags and exact time of event occurrence. Range is from -2147483648 to +2147483647. 

  4. 16-bit with flag and time – frozen counter event is reported to master as signed 16-bit integer with quality (status) flags and exact time of event occurrence. Range is from -32768 to +32767 

Event hysteresis: 

Event hysteresis refers to a mechanism used to prevent the generation of redundant event messages due to any disturbances. This is particularly with counters, where frequent changes can lead to many events being reported to the DNP3 master. Implementing hysteresis helps to reduce the communication load and ensures that only significant changes in the counter value are triggered as events. A predefined limit at input “Event Hysteresis” must be exceed before an event is generated.