Note that the M90 series does not offer RS485 communications, except via external converter.
Certain M91 OPLCs can be ordered with an RS485 port. Within the controller, the jumper settings determine the COM port function according to RS232 or RS485; RS485 termination settings are also determined via jumper.
To check if your controller was supplied with an installed RS485 port, check the device’s model number.
For more information regarding M91hardware COM settings, check the topic RS485 Options.
The value of SI 64, Set COM Port Mode, determines if the port will function according to RS232 or RS485. When SI 64 contains 0, the port is set to RS232, when SI 64 contains 1, the port is set to RS485.
The value in SI can only be changed via Power-up, whether via the Ladder application or by setting a Power-up value for SI 64.
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In order to change the mode, Power-up must take place; as for example if the power cable is temporarily disconnected. |
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By factory default, SI 64 contains 0. |
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When a port is set to RS485, both RS232 and RS485 can be used simultaneously if flow control signals DTR and DSR are not used. |
Jazz controllers do not comprise integral COM ports. Ports may be added via Add-on Port modules. Such modules are plugged into the Jazz Jack. Examples of such ports include the MJ20-PRG RS232 Programming Add-On Port and the MJ20-RS Add-on Module.
The MJ20-PRG enables you to establish PC-PLC communications, download programs, and to communicate with RS232 devices that supply active (RS232 positive voltage) DTR and RTS signals.
The MJ20-RS, available by separate order as part of the JZ-RS4 kit,-enables Jazz OPLC™ networking and serial communications, including program download. The module comprises:
A single communication channel that serves one RS232 port and one RS485 port. The module cannot communicate via RS232 and RS485 simultaneously.
Switches that enable you to set the device as an RS485 network termination point.
Note that the ports are isolated from the Jazz OPLC.
In order to switch between RS232 and RS485, you must use Special Function 310, as explained in the topic Change COM Port Parameters.