Author Topic: "dual Modbus Master/Slave  (Read 5928 times)

Alan

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"dual Modbus Master/Slave
« on: April 13, 2003, 04:24:16 PM »
Is it possible to configure Com1 for Modbus RTU slave (modbus address 1 or above on T100MD+) and send "WriteModbus()" and "ReadModbus()" commands to other slaves in the network from the same port?

Will this unit be able to respond to SCADA queries for data as a slave and still be able to send occational Master commands to other slaves?  I'm using RF to communicate to  the slaves in the network from this unit to the remote slaves.

In other words, can the TM100MD+ be schizofrenic?

Thanks,

Alan
« Last Edit: December 31, 1969, 04:00:00 PM by 1076562000 »

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Re: "dual Modbus Master/Slave
« Reply #1 on: April 14, 2003, 12:14:39 PM »
Yes, as long as the PLC program is not actively sending any modbus command out of COM1, the communication port is immediately available as a slave port. i.e. the same comm port can work both as a master and a slave.

You will have to take care of the "arbitration" issue, meaning that you have to ensure that the PLC will not talk on the COM1 when it is supposed to listening to incoming command. Otherwise a collision will occur and both incoming and outgoing command will be lost.
« Last Edit: December 31, 1969, 04:00:00 PM by 1076562000 »
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