Background scan

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 transfer. The valid ASDU type IDs are listed in the compatibility list for the station (table type ID <-> cause of transfer). 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 is to be transferred as a background scan must be configured with the Group flag: IEC870_GRP_BACKGROUND.

Sample:

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