Supplement operating manual for DREHMO i-Matic actuators with integrated
MODBUS fieldbus interface
Wenden, 21.03.12
Page 10 of 18
Prepared by: Ste
2.4 Parameterisation
The modbus relevant settings can be changed menu driven using the local control unit. The
parameters are to be found in the menu tree under Menu\Parameters\Interface\Modbus.
2.4.1 Communication settings – addresses, baud rate, parity
The slave address can be set in the range between 1 and 247. In case of redundancy, the
address has to be set for both channels. The baud rate settings are done by a selection of
the required and available value out of a lookup table. The parity can be set to even, odd or
none. The number of stop-bits are set automatically according to the selected parity setting.
2.4.2 Number of channels – bus profile
The actuator can be ordered with a redundant modbus channel. In this case, the parameter
bus profile
is set to redundant by the manufacturer, otherwise to standard.
2.4.3 Redundancy modes – line redundant vs. master redundant
In case of a redundant interface card, it is possible to set up two different redundancy
modes. The different modes have a different reply behaviour.
For line redundant mode, it is possible to block the reply of the inactive channel by setting
the parameter redundancy reply to “Active channel”. This is necessary, if both channels use
the same bus line with the same address setting.
In master redundant mode, the parameter has to be set to “both channels”.
For both modes, the behaviour of channel select and switch over is the same. On start-up,
the actuator selects the first valid channel as active channel. If the communication on this
channel fails, the actuator switches to the other channel after the timeout is expired – for
description of timeout settings see description of fail-safe.
Only if none of the channels is valid, the fail-safe mechanism becomes active (if activated).
An active switchover to the other channel can be forced by setting a high to low transition
on the special bit in the cyclic data stream.
2.4.4 Function Fail-Safe – Timeout setting
Once a bus communication was established, a fail-safe mode is available if the actuator is
in remote mode. This fail-safe mode becomes active, if the communication is no longer
active, and the set
timeout
is exhausted. The
timeout value
can be set in units of
