Rosemount TankRadar Rex DAU 2100, Service Manual

Page: 34 / 154

Rosemount Tank Radar Rex
Chapter 3 Device Description
3-20
Service Manual
308012En, Ed.2
May 2013
3.2.3 Software
The FCU software controls the
collection of data from the units
connected to the Field Bus, and
handles the distribution of data
to the TankMaster PC on the
Group Bus.
The Group Bus Process and the
Field Bus Process work as
interfaces to the serial
communication control, SCC.
The EEPROM switch is used by
the program to determine if it is
allowed to write to the
EEPROM. The watch dog has
to be gritted at least every tenth
second or else a reset is
performed. Direct Memory
Access (DMA) channels in the
FCU microprocessor are used
to write to the SCC.
When the Group Bus Process receives a query from the master on the
Group Bus, it will translate the query into the MODBUS format if
necessary. The query is processed, translated back to the original format
and the response is sent back to the master. The processing of the query
could be done in the Field Communication Unit or it could request further
processing in the slave units (RTGs and DAUs) connected to the Field
Communication Unit.
The Field Bus Process scans the slave units as a master. The result of
the queries is stored in the standard data registers. It could also get
queries from the Group Bus, via the Special Command Process, to be
sent out on the Field Bus. The results of those queries are stored in the
Special Data Buffer.
3.2.4 Redundancy
In order to reduce the risk of communication failure between the
TankMaster and the units connected to the TRL/2 field bus, two FCUs
can be connected to run in parallel. If one FCU fails, the other one
automatically takes over without any action from the operator. The FCUs
are connected with an extra cable allowing them to communicate. The
inactive FCU constantly checks if the connected FCU is active. If the
active FCU fails, it signals to the backup FCU to take over. Then the
backup FCU immediately switches to an active state.
Master
Slave
Master
Slave
Tank-
Master
FCU
RTG/DAU
Group
Bus
Field
Bus
Figure 3-14. Group and Field bus
communication