The Field Communication Unit (FCU) is a data

concentrator that continuously polls data from field

devices such as radar level gauges, Data Acquisition

Units and Remote Display Units and stores

values in a buffer memory. Whenever a request for

data is received, the FCU can immediately send

data from a group of tanks from the updated buffer

memory.

The FCU acts as a slave on the group bus

and as a master on the field bus. The unit has

six communication ports. These ports can be

individually configured as either group bus ports or

as field bus ports according to one of the alternatives

An interface board can be connected for each

communication port. These boards can be either

FCM boards for the TRL2 Bus or FCI boards for

RS485 communication. Two group bus ports can

also be configured as RS232 by connecting a

jumper connector instead of an FCM or FCI board.

As standard the Field Communication Unit is

delivered with six FCM boards and two RS232

jumper connectors.

Each device has an individual address on the field

bus except for the RDU 40 which uses the same

address as the RTG it is connected to.

Two FCU:s can be connected in parallel with one

unit operational and one working as “hot” redundant

backup for the other. The units are software

monitored and the backup unit is automatically

triggered and activated in case of primary unit

failure. See page 41 for more information.