hi all,

i am getting a modbus error illegal data address (01 83 02 C0 F1) When i try to read from the holding registers. this is happening with the switch at position 2 from the twido cable. when switch is at any other position, no responce is coming from the PLC.

i am using DAQfactory, and modbus tester, any idea of how i can get aound this?

 

If you want to test with a different Modbus Master for reference, check out http://www.automatedsolutions.com.

Fully functioning evaluation copies of our ActiveX Controls and OPC Servers with ready-to-run HMI applcations are available for download.

 

You have to ensure that the Twido PLC memory area is set large enough to read values up to the memory size. Default is "Auto" that sets a size as you program. You can manually set the size as well (PLC/Memory Use/Edit/Memory Words).

Your lead should also work at position 3. Position 2 sets a link in the connector to force the Twido to communicate to suit the programmer. You also may not have set the port away from the default "Remote Link" mode. The Help file covers this.

 

Dear Sir,

I am a Zambian student doing my project on Modbus and experience the same problem, I would highly appreciate if you could give me a direction.

I am using an TWDLMDA20DTK Telemecanique PLC but it seems that I am only able to get a sensible reply on the identification code (2B) Modbus command. All the other commands (except for the diagnostic one (08 00)) give me the same error message 8 (8x).

The setting of cable seems to be allright, the memory usage seems OK, communication is set for MODBUS, but still it seems I can t read the registers of the PLC.
For example when sending the command read coil
01 adress PLC
01 read coil
00 high adress
00 low adress
00 high bits
01 low number of bits
crc

I get as reply
01
81
02
c1
91

The PLC is in the RUN mode and a small program is downloaded. But I tried it in all possible combinations with no avail.

I become a bit desperate because the end of the academical year is approaching very fast.

Sincere regards from Zambia,

Sankalimba