Citect - Modbus - Unitronics

M

Thread Starter

Marek

hi,
I have a problem with configuration Citect with PLC Unitronics using MODBUS. I`m using MODBUS RTU with RS-232. I have set every settings in Citect Scada 7.20 (boards, ports, servers, cluster, user name) but I don`t know, what should i write into Citect.ini.

I know, that, in this file i should define [MODBUS] InitType or InitUnitAddress or anything else, but, I don`t know, how numbers should I set. In this file is nothing about MODBUS. Should I write anything else about this problem?? In Citect can I see only #COM. Sorry for my english.
 
1) Lots of PLCs have RS-232 ports, but don't talk Modbus. Just having a COM port is no guarantee that the device support Modbus RTU, unless the documentation says the device supports Modbus RTU.

2) Ensure that the Unitronics' RS-232 port is actually configured for Modbus RTU. On many devices, the RS-232 ports can be configuration ports or communications ports, sometimes dedicated to one function or the other, sometimes configurable as to its function.

To get a definitive answer as to whether the device supports Modbus and what the COM port functions are, either read the manual, get tech support to answer, or maybe someone on the forum familiar with "Unitronics PLC" will pipe up with an answer.

3) Configure the Unitronics COM port.
I haven't programmed a Unitronics, but I would suspect that there is a COM port settings dialogue box somewhere in the development software. Try the Help file. COM port settings are typically where the baud rate, word size and parity are established and sometimes where the port's function is defined.

4) PLC's can frequently be a Modbus slave or a Modbus master. Citect wants to be the master, so the Unitronics should be a slave.

5) How is the Modbus slave map populated? The data in the Unitronics have to be associated with Modbus slave registers, or populate the slave map. Modbus mapping is specific to Unitronics. Again, check the documentation.

6) Figure out whether you need a null modem adapter on the RS-232 line. Check the pinout of the RS-232 port to see whether Tx pin will go the PC's Rx pin with a straight cable. If not, use a null modem adapter or cable.

7) Force known, non-zero values into 3 adjacent, contiguous Unitronics registers and try to read the middle one with Citect. You'll either get nothing (typically a time-out or comm not established) probably because there's an issue with the RS-232 or the ports, or you'll get a value.

If the value isn't what you expect, it might be one from either adjacent register, indicating to you that you'll have to one-offset your addressing, or the number could be wildly wrong, indicating that the data format needs tweaking, or both.

8) Depending on how convenient it is to rapidly change settings in Citect when working to establish communications with the Unitronics slave, it might warrant using one of the generic Windows Modbus masters, like Simply Modbus, Modscan32 or Modbus Poll, to confirm that the comm link is working, the wiring is correct, the COM ports are functional, and the data formats are correct.

9) If the Unitronics does indeed do all of this in a .ini file (stranger things have happened), then the syntax and format for such settings HAVE to be documented. You need to find it, wherever it is.
 
thanks a lot. I have solved my problem. I must set Cluster in Citect SCADA with the same name, who is in the file citect.ini. I think, that is the same name who is in the project Example. When I did this, I can connect PLC with SCADA using MODBUS.
 
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