RS485/MODBUS Protocol E-1
MN767S
Appendix E
RS485/MODBUS Protocol
E.1 Introduction
The VS1STS AC Drive is supplied with imbedded RS485 communications that supports the Modbus-RTU protocol. This
allows the user to set up a multi-drop communications network between multiple VS1STS drives and a PLC or host
computer without the requirement of option boards for the drives. This is a master-slave architecture where the master (e.g.
PLC) can monitor and control multiple VS1STS drives on the same network with other Modbus-RTU slaves. This appendix
defines the specifics needed to set up a VS1STS on an RS485 network running the Modbus-RTU protocol and documents
the function codes and exception codes supported by the VS1STS. For a complete definition of the Modbus-RTU protocol
and the content of specific messages see www.modbus.org.
E.2 Installation
1. Connect the RS485 communication line to RJ11 connector, (see Chapter 5).
2. Check the connections and turn ON the inverter.
3. Table E-1 documents the parameters within the VS1STS that are related to communications:
Table E-1 Communication Parameters
Number
Name
Comments
P1-07
Start/Stop Source
Set to 4 for applications that require network control to start and
stop the drive over the network
P2-26
Baud Rate
Select the baud rate utilized by the master device on the network.
All devices on the network must utilize the same baud rate.
P2-27
Drive Address
Set to the desired Modbus-RTU address (note that each device
on the network must have a unique address).
P2-28
Master/Follower
Select drive to be the master line reference or a follower section.
P2-29
Follower Reference Scale
Factor
Set a percentage scale factor for the follower drive to
proportionally run faster or slower than the master reference.
4. Make connection to the master and other slave devices. The maximum number of drives that can be connected is 31.
Maximum length of communication line is 2300 ft (700m).
E.3 Operation
1. Remove all power from the VS1STS control.
2. Disconnect the motor load from the control (terminals U, V and W). (Do not connect the motor load until stable
communication between the master controller and the inverter are verified.)
3. Verify master controller and the inverter connections.
4. Turn ON the inverter.
5. Start the communications program on the master controller.
6. Verify proper communications and that the VS1STS is controlled as desired.
7. Remove all power from the VS1STS control.
8. Connect the motor load to the control (terminals U, V and W).
9. Turn ON the inverter.
10. Verify proper operation. See Troubleshooting at the end of this section to aid in resolving any remaining problems.
E.4 Performance Specifications
Table E-2 Communication Performance
Communication Method
RS485 Hardware specification, MODBUS protocol
Transmission Form
Bus method, Multi drop Master/Slave architecture
Applicable inverter
VS1STS series
Connectable drives
Max 31
Transmission distance
Max. 2,300 ft (Repeater may be required for high noise environments.)
Summary of Contents for VS1STS Series
Page 1: ...10 11 Installation Operating Manual MN767S VS1STS AC Microdrive ...
Page 6: ...iv MN767S ...
Page 28: ...5 8 Control Wiring MN767S ...
Page 50: ...8 2 Customizing Your Application MN767S ...
Page 54: ...9 4 Troubleshooting MN767S ...
Page 56: ...A 2 Technical Specifications MN767S ...
Page 68: ...D 2 Options and Kits MN767S ...