Cyclic data transmission

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Cyclic data transfer is initiated in a similar way as the background scan from the substation. It is independent of other commands from the central station. Cyclic data transfer continuously refreshes the process data of the central station. The process data are usually measured values that are recorded at regular intervals. Cyclic data transfer is often used for monitoring non-time-critical or relatively slowly changing process data (e.g. temperature sensor data). Cyclic/periodic data are transferred to the central station with cause of transmission <1> periodic/cyclic. The valid ASDU type IDs are listed in the compatibility list for the station (table type ID <-> cause of transmission). Cyclic data transfer can be configured via the system parameters and the configuration parameters of the application objects.

Configuration of the system parameters:

bPerCyclic      : BOOL := TRUE;
tPerCyclicBase  : TIME := T#60s; 

The first parameter activates cyclic transfer. The second parameter is the base time for the cyclic/periodic data transfer (in this case 60 seconds).
 

Configuration of the application objects:

• IEC870_GRP_PERCYC group parameter has to be set;
• The multiplier parameter (multiplier) of the F_iecInitAOEntry function has to be set to a zero <> value. Example: With a multiplier = 2 and a base time of 60 seconds the process data of the application object are sent to the central station every 120 seconds.

Example of measured value configuration. The value must be transferred every 120 seconds to the central station (measured value, normalized value without time tag, M_ME_NA_1).

F_iecInitAOEntry( M_ME_NA_1, 222, IEC870_GRP_INROGEN OR IEC870_GRP_PERCYC, 2, MAP_AREA_MEMORY, 6, 0, AODB[2] );