Commands and signals of the Modbus RTU interface
OPEN, STOP, CLOSE, position setpoint, RESET, EMERGENCY operation command
Process representation output
(command signals)
●
End position OPEN, CLOSED
●
Actual position value
●
Selector switch in position LOCAL/REMOTE
●
Torque switch OPEN, CLOSED
●
Limit switch OPEN, CLOSED
Process representation input (feed-
back signals)
●
Motor protection tripped
●
Torque switch tripped in mid-travel
Process representation input (fault
signals)
The behaviour of the actuator is programmable:
●
Stop in current position
●
Travel to end position OPEN or CLOSED
●
Travel to any intermediate position
●
Execute last received operation command
Behaviour on loss of communication
General data of the Modbus RTU interface
Modbus RTU according to IEC 61158 and IEC 61784
Communication protocol
Line (fieldbus) structure. When using repeaters, tree structures can also be implemented. Coupling and
uncoupling of devices during operation without affecting other devices is possible.
Network topology
Twisted, screened copper cable according to IEC 61158
Transmission medium
EIA-485 (RS-485)
Fieldbus interface
Line topology:
Possible cable length with repeat-
er (total network cable length):
Max. cable length (segment
length) without repeater
Baud rate (kbit/s)
approx. 10 km
1,200 m
9.6 – 38.4
Redundant loop topology
Max. possible cable length of re-
dundant ring
Max. cable length between actuat-
ors (without repeater)
Baud rate (kbit/s)
approx. 290 km
1,200 m
9.6 – 38.4
Transmission rate/cable length
Modbus slave, e.g. devices with digital and/or analogue inputs/outputs such as actuators, sensors
Device types
32 devices without repeater, with repeater expandable to 247
Number of devices
Polling between master and slaves (query response)
Fieldbus access
Read Coil Status
01
Supported fieldbus functions
Read Input Status
02
Read Holding Registers
03
Read Input Registers
04
Force Single Coil
05
Force Multiple Coils
15 (0FHex)
Preset Single Register
06
Preset Multiple Registers
16 (10Hex)
Report Slave ID
17 (11Hex)
Diagnostics:
●
00 00 Loopback
●
00 10 (0AHex) Clear Counters and Diagnostic Register
●
00 11 (0BHex) Return Bus Message Count
●
00 12 (0CHex) Return Bus Communication Error Count
●
00 13 (0DHex) Return Bus Exception Error Count
●
00 14 (0EHex) Return Slave Message Count
●
00 15 (0FHex) Return Slave No Response Count
●
00 16 (10Hex) Return Slave NAK Count
●
00 17 (11Hex) Return Slave Busy Count
●
00 18 (12Hex) Return Character Overrun Count
08
44
SVM 05.1 – SVM 07.5 / SVMR 05.1 – SVMR 07.5
Technical data
Modbus RTU
