Internet PLC Forum
General => Technical support => Topic started by: tkidder on June 13, 2004, 09:26:48 AM
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Have been trying to interface t100md to magelis XBT200 display thru com 3. The display uses modbus
protocall. I have tried using "writemodbus 3,1,1001,1234"
to talk directly to a field on the Magelis. I have tried
many other addresses. also using the Magelis as the
modbus master. Have not had any luck.
any help would be greatly appreciated
Thanks.
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The most important thing is to ensure that the PLC's comm 3 is set to the same baud rate and communication format as your device. Default is 38400,8,1,n but you can change it using the SETBAUD 3,xx command.
"writemodbus 3,1,1001,1234" will write the 16-bit data "1234" to MODBUS holding register 41002. But sure that this is actually the target address of interest.
Since the COMM port parameter is "3" it uses MODBUS ASCII protocol . Most likely your device is using MODBUS RTU protocol. So in that case, you should change your statement to "writemodbus 13,1,1001,1234".
The number "13" tells the CPU to use MODBUS RTU protocol instead of MODBUS ASCII protocol. The two protocols are formatted differently and cannot be mixed.
Note that WRITEMODBUS uses only the modbus function 03. Make sure that your device support function 03.