Transmission Modes
Original instructions
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Introduction
With DNP3 or IEC 60870-5-101/104 protocols, the advanced RTU module manages different ways of retrieving data with the following transmission modes:
NOTE: For transmission modes setup, set the Advanced Parameters (DNP3).
Balanced and Unbalanced Mode
In the unbalanced transmission mode only the master station can initiate data transfer with the remote devices by polling the slaves. In balanced transmission mode, both the master and slaves can initiate data transfer.
Polled Interrogations
Polled Interrogations is the basic data exchange method. The master station requests data to multiple RTU station devices by polling periodically the remote slaves.
Report by Exception
Report By Exception (RBE) provides optimized data transfer between master and slaves stations, where only changes of data are reported, whereas in Polled Interrogations - the master station periodically requests data to the slaves devices. RBE is particularly useful when using low rate communication media (PSTN, GSM/GPRS) by reducing traffic overhead and transmission costs.
Unsolicited Messaging
Unsolicited Messaging is the basic data exchange method. The slave station initiates data transmission even though the master station does not send poll interrogations.
Parameters Dependency Link
Parameter dependency link table for IEC 60870-5-101/104:
Transmission Mode
Parameter Dependency
Parameter Location
Relationship With Transmission Mode
Balanced and Unbalanced Mode
Used Balanced Mode
IEC 60870-5-101 Slave/Channel/
Unbalanced transmission mode: Only an IEC 60870-5-101 master station can initiate data transferring with the remote devices by polling the slave. It means that slave keep silent unless master request its response. RBE is not recommended to use under this mode.
Balanced transmission: Both the master and slaves can initiate data transfer. IEC 60870-5-104 supports balanced mode by default thanks to TCP/IP.
Polled Interrogations
Groups
IEC 60870-5-101 Slave / Channel/Session/Sector/
Data Mapping/M_xxx
It is to set group attributes of monitoring point. It is used to respond to the general Interrogations with specific group of static data.
IEC 60870-5-104 Server / Channel/Session/Sector/
Data Mapping/M_xxx
Read Time Format
IEC 60870-5-101 Slave / Channel/Session/Sector/
Parameter
It is used to specify the time stamp format in the response to read command.
NOTE: It is used for the points except measured points and counter.
IEC 60870-5-104 Server / Channel/Session/Sector/
Parameter
C_RD_NA Measure and Time Format
IEC 60870-5-101 Slave / Channel/Session/Sector/
Parameter
It is used to specify the time stamp format in the response to read command.
NOTE: It is used for measured points
IEC 60870-5-104 Server / Channel/Session/Sector/
Parameter
C_IC_NA Time Format
IEC 60870-5-101 Slave / Channel/Session/Sector/
Parameter
It is used to specify the time stamp format in the response to read command.
NOTE: It is used for counter.
IEC 60870-5-104 Server / Channel/Session/Sector/
Parameter
Report By Exception
Max Event Count
IEC 60870-5-101 Slave / Channel/Session/Sector/
Events/M_xxx
Event count is disabled by default. It is required to set explicitly for RBE.
When Event count is more than 0, the advanced RTU module saves events into local buffer. After connection is ON Line, the event is reported automatically.
IEC 60870-5-104 Server / Channel/Session/Sector/
Events/M_xxx
Delete Oldest Event
IEC 60870-5-101 Slave / Channel/Session/Sector/
Advanced Parameter
It is used to manage event buffer overflow. Delete the oldest one or newest one when buffer overflow.
IEC 60870-5-104 Server / Channel/Session/Sector/
Advanced Parameter
Event Generation
IEC 60870-5-101 Slave / Channel/Session/Sector/
Data Mapping/M_xxx
It is used to specify whether this point is reported as event or not.
NOTE: It must be checked for RBE.
This feature is available for advanced RTU module firmwareV1.7 or later.
IEC 60870-5-104 Server / Channel/Session/Sector/
Data Mapping/M_xxx
Parameter dependency link table for DNP3:
Transmission Mode
Parameter Dependency
Parameter Location
Relationship With Transmission Mode
Balanced and Unbalanced Mode
Unsolicited Message feature
—
DNP3 support balanced mode by default for both DNP3 and DNP3 NET. When DNP3 over Serial Line, master need manage to enable/disable the unsolicited message. In general, keep unsolicited message managed by master or disabled if master has multiple slave communicated over serial line.
When DNP3 over TCP/IP, no such strict ion on the management of unsolicited message thanks to TCP/IP.
Polled Interrogations
Event Class Mask
DNP3 Slave / Channel/Session/
Data Mapping/{Binary input/output/counter, Analog input/output}
It is mandatory to enable Class 0 to respond to Integrity Poll of controlling station.
NOTE: It is possible to read all data through Read Group no matter what class it is assigned.
DNP3 NET Server / Channel/Session/
Data Mapping/{Binary input/output/counter, Analog input/output}
Unsolicited Message
(Report By Exception)
Unsol Allowed
DNP3 Slave / Channel/Session/
Advanced Parameter
It is used to enable/disable unsolicited message by controlling station.
For unsolicited message, it must be enabled.
Unselected Unsol Allowed is to control not to report event as unsolicited message, but the events are able to report for integrity poll and read group.
DNP3 NET Server / Channel/Session/
Advanced Parameter
Max Event Count
DNP3 Slave / Channel/Session/
Events /{Binary input/output/counter, Analog input/output}
Event count is disabled by default. It must be set as enabled explicitly for unsolicited message.
When Event count is more than 0, the advanced RTU module saves events into local buffer which are able to report as unsolicited message if unsolicited message is enabled, or respond to integrity poll and read group.
DNP3 NET Server / Channel/Session/
Events /{Binary input/output/counter, Analog input/output}
Delete Oldest Event
DNP3 Slave / Channel/Session/
Advanced Parameter
It is used to manage event buffer overflow. Delete the oldest one or newest one when buffer overflow.
DNP3 NET Server / Channel/Session/
Advanced Parameter
Unsolicited Message
(Report By Exception)
Event Class Mask
DNP3 Slave / Channel/Session/
Data Mapping/{Binary input/output/counter, Analog input/output}
It is mandatory to assign one of Class 1,2,3 and Unsolicited for unsolicited message. The advanced RTU module initiates unsolicited messages as class according to unsolicited message enabled by controlling station.
NOTE: It is possible to read all events through Integrity Poll/Read Group no matter whether unsolicited message is enabled or not.
DNP3 NET Server / Channel/Session/
Data Mapping/{Binary input/output/counter, Analog input/output}
Unsol Class x Max Event
{x=1,2,3}
DNP3 Slave / Channel/Session/
Advanced Parameter
It is used to specify the maximal number of events in the corresponding class to be allowed before an unsolicited response is generated if unsolicited message is enabled.
NOTE: Once one class matches the maximal number of events, the events of all classes enabled are sent out.
DNP3 NET Server / Channel/Session/
Advanced Parameter
Unsol Class x Max Delay
{x=1,2,3}
DNP3 Slave / Channel/Session/
Advanced Parameter
It is used to specify the maximal amount of time after an event in the corresponding class is received before an unsolicited response is generated if unsolicited message is enabled.
NOTE: Once one class matches the maximal amount of time after event generation, the events of all classes enabled are sent out.
DNP3 NET Server / Channel/Session/
Advanced Parameter