crc error in modbus communication

Hi, i initialize the port 0 of my cpu 226 as a slave but when i open modscan which acts as a master the din bit is high and on error bit i recieved 7 which means CRC error can any one help me out regarding this,

Attached is the programm and modscan software, kindly help me.

v3nom

Hi, i initialize the port 0 of my cpu 226 as a slave but when i open modscan which acts as a master the din bit is high and on error bit i recieved 7 which means CRC error can any one help me out regarding this,

Attached is the programm and modscan software, kindly help me.

 Is there anyone who can solve this problem???

I also have a same problem with this.....

Hello,

can you confirm all communication parameters set same on both systems? You can post zip-ed pictures which can show some situation, maybe from code with online values, then we can better see what problem can be.

Duris_I

Hello,

can you confirm all communication parameters set same on both systems? You can post zip-ed pictures which can show some situation, maybe from code with online values, then we can better see what problem can be.

Thank you for having interests in my question.

Here I uploaded my PJT.

During mornitoring, I can see the error code 7 "receive CRC error".

- CPU 226 / Configured as Modbus Slave / Baud Rate 19,200 / Data bit 8 / Stop bit 1 / Parity none 

Best Regards.

Hello,

have looked to your project, looks ok to me in first short look, but that INIT of MB can be executed only once I think. What master device asked your CPU? Is PC simulation SW or real device? I recommend to you run some PC application (it must not be true MB Slave application if you're MB skilled) in place of PLC and check received request consistency. It can contain needed info how/what Master requesting. In case of your error code this is needed check that Master message. Another solution can be oposite situation, run some PC application as Master and poll your CPU. In this case you must know what you want ask due your PLC data available. Of course, I can expect also some real wire line problems, but expect you'va already done check this. For first I'll be check that communication if all is ok.

Thank you for helping me.

That program I've got from my service provider but they didn't reflect the communication with our device (terminal server as master_Manufacturer: Systech) for Honeywell System. Then they disappeard :(......

So I added Mbus Init and also Mbus_Slave module after check the manual.....

Anyway I tried to get communication response from CPU 226 using my PC as attachment.

I asked to response I0.0 (address : 10001) and also tried to get response Q0.0 (address 00001):  

With this way in attachment, I've got no.7 error (receive CRC error) in mbus_slave module when my PC poll to cpu 226.

Best Regards.

Hello,

look pls again to help about MB_Init block. As I've sugested, this init block can be executed only once, on first scan - SM0.1 bit enable this block, look to help. Slave block can be executed every scan. Do you have LED indications on that RS-485 to RS-232 converter? In not SEND/RECV time, that LEDs can be off, only if PC application send requests or PLC responds, the exact LED will be on. In case you not send or recv and some LED on converter is permanently on, this is problem with swapped wires on 485 side, you need change them. You can also set some Delay time for sure, make tests. Sry, don't work with that Modscan SW so no help here about functionality. Also functionality test of that converter can be made for sure, no luck without it's functionality!

Duris_I

Hello,

look pls again to help about MB_Init block. As I've sugested, this init block can be executed only once, on first scan - SM0.1 bit enable this block, look to help. Slave block can be executed every scan. Do you have LED indications on that RS-485 to RS-232 converter? In not SEND/RECV time, that LEDs can be off, only if PC application send requests or PLC responds, the exact LED will be on. In case you not send or recv and some LED on converter is permanently on, this is problem with swapped wires on 485 side, you need change them. You can also set some Delay time for sure, make tests. Sry, don't work with that Modscan SW so no help here about functionality. Also functionality test of that converter can be made for sure, no luck without it's functionality!

 Thank you for your reply.

I changed MB_Init block with SM0.1 and also check everything you told me. But still I have error no. 7 :(

Is there any other reason???

Best Regards.

Hello,
when you get error 7 constantly, there is for sure an error in parameterization or wiring.

Regards,
Kaulquappe

Dear All.

I am facing somewhat same problem.

i have no errors in the MB blocks. it shows "0" in both blocks.

But in MB_Slave block Done bit is not active and when i check it in simulator ModScan32 it is saying

"Checksome Error In Response Message"

"Modbus Exception Response From Slave Device"

i have no idea what i am doing wrong.

Can any one help me.