Engineering large plants - Basic Documentation - RMK770-1

Communication via the KNX bus

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Engineering with ACS

The ACS790 software is recommended to engineer large plants, as it can be used to set all necessary addresses and configuration values.


1. Addressing of area/line couplers and IP router.

2. Set device addresses at bus devices.

3. Additional settings for the IP network in the IP router via ACS790
(see below).


If the area/line couplers and IP routers are addressed before the bus devices, the bus devices are ready to receive the "area" and "line" components of the address.


To keep communication to a minimum, filter setting "Normal (route)" should be retained.

IP address assignment

IP routers are factory-set to obtain their IP address from a DHCP1) server.

ACS allows for manual assignment of the IP address.

1) Dynamic Host Configuration Protocol. DHCP is a client-server protocol that reduces the time and effort required to assign IP addresses.

IP settings

Other IP settings in ACS:

  • IP routing, multicast addresses

  • IP subnet mask

  • IP standard gateway

Engineering with ETS

When using the ETS engineering tool, e.g. in plants with third-party devices, the ETS product database of Synco bus devices must be imported into ETS.

Note especially the following when engineering with ETS:

  • ETS does not allow access to the LTE filter table (to filter zone addresses).

  • ETS allows access to the S-Mode filter table (to filter group addresses).

  • Fixed group addresses are defined in the KNX standard for some system functions, including, e.g., group address 30/3/254 for the system time and 30/3/250 for fault information.

  • Group addresses30/3/254 and 30/3/250 are factory-set in the Synco bus devices.


When downloading new group addresses into Synco bus devices, the group addresses 30/3/254 and 30/3/250 referred to above must be set up in the ETS tool and connected. Only then can the download be initiated.

Without group address 30/3/254 and a connection for the system time, the time between the Synco bus devices after the first download can no longer be synchronized.

If a different group address is used for the system time, this group address must be entered and downloaded to all devices with system time communication (master and all slaves).

It is not possible to set up group address 30/3/xxx (main group 30) in ETS with default values. However, it is possible to enable the setting of main groups > 15 via the Windows registry. Please address questions about the required entries for this purpose to your ETS supplier.

The special group addresses can also be downloaded via the HIT Info Center -> Product Overview -> Synco ( and imported in ETS.