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MODBUS enables you to establish master-slave communications with any connected device that supports the MODBUS protocol. Any controller in the network may function as either master or slave using any of the controller's existing COM Ports.
Unitronics currently supports MODBUS in the following transmission modes:
RTU (binary)
| M91 | The M91 series supports MODBUS via built-in COM ports |
| Jazz | Although Jazz PLCs do not comprise built-in COM ports, Jazz can support MODBUS if you install an appropriate add-on port module, available separately. |
| M90 | The M90 series does not support MODBUS |
| Jazz | Jazz 2 controllers can support Ethernet via an Add-on Port module plugged into the Jazz Jack. For more information, refer to the topic Ethernet: Jazz_2_only. Via this port, you can run MODBUS commands over Ethernet. |
Note that:
- Communications capabilities are determined by the type of Add-on Module.
- Default COM settings and pin-outs are given in the technical specifications of the relevant Add-on Port.
- The MJ20-PRG Programming Port may be used for RS232 communications with devices that supply active (RS232 positive voltage) DTR and RTS signals
The slave addressing for this series are as follows (decimal):
Since there are no Ladder elements for MODBUS functions; you perform them by storing values into Sis.
You can find more information regarding this subject on U90 Ladder help file under Home > Communications > MODBUS.
You may also find example on the help menu under examples.