Background scan

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The background scan is used for refreshing the process information sent from the substation to the central station as an additional safety contribution to the station interrogation and for spontaneous transfers. Application objects with the same type IDs as for the station interrogation may be transferred continuously with low priority, and with <2> background scan as the cause of transmission. The valid ASDU type IDs are listed in the compatibility list for the station (table type ID <-> cause of transmission). The background scan is initiated by the substation and is independent of the station interrogation commands.

Configuration of the system parameters:

The transfer cycle is specified via system parameters in the substation.

bBackScan := TRUE;
tBackScanCycle := T#30s;

Configuration of the application objects:

Application objects whose process data are to be transferred as a background scan have to be configured via the IEC870_GRP_BACKGROUND group flag.

Example:

F_iecInitAOEntry( M_SP_NA_1, 100, IEC870_GRP_INROGEN OR IEC870_GRP_BACKGROUND, 0, MAP_AREA_MEMORY, 100, 0, AODB[0] );