8 Station variants8.3 How the "station variants" operating mode works358 Gateway XN-312-GW-CAN 06/16 MN050003-DE www.eaton.eu6. If this checksum matches one of the checksums on the PLC, this meansthat the selected station variant on the gateway is permitted and can beused.7. If the checksums do not match, the actual configuration will be readfrom the gateway. The actual configuration will then be compared withthe permitted station variants found in the list on the PLC.8. If the PLC finds a matching station variant, it will load the correspondinglist onto the gateway. If it does not, the PLC will delete the list on thegateway.8.3.1 General principles / behavior of the gateway and the PLCAs soon as the config check is active, it will always be carried out regardlessof the station variant. Please note that the config check is used to checkwhether the actual configuration matches the target configuration that hasbeen stored – the check for permitted station variants is carried out after-wards.What happens if the "station variants" operating mode is enabled?• On the field bus side, the gateway will behave as though the full configu-ration were physically connected. The address mapping used will bebased on the full configuration.• Attempts to access variable values from missing nodes will return anundefined value.• Outputs written with the use of PDOs will not be set until the PLC hasconfirmed the selected station variant by writing the checksum back tothe gateway.When will the gateway exit "station variants" mode?The gateway will exit the "station variants" operating mode and delete its listsfor the full configuration and for the selected station variants when one of thefollowing events occurs:• A change to the actual configuration for the XN300 slice modules isdetected on the gateway.• The gateway receives a start-remote-node command without the enablesignal for the "station variants" operating mode being activated before,i.e., "Activation StationVariants Mode" = FALSE.How does the enable process in which the PLC sends an enable signalwork?The function block (FB) asks the gateway for the checksum. After receivingthis checksum, the FB checks whether one of the station variants stored onthe PLC has the same checksum as the station variant on the gateway (this￫ Please note that if the config check is active and you want to puta different station variant into operation, you will first need tostore the new station variant as a target configuration in thedevice's memory ￫ "Switching the gateway on with a configcheck" section on page 38.
