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MN4000/MN4100 Modbus Problem

Home Technical Q&A MN4000/MN4100 MN4000/MN4100 Modbus Problem

MN4000/MN4100 Camera Troubleshooting

Symptoms:-  After connecting to the camera on  i/p xxx.xx.xx.xxx port 502 using Modbus TCP the camera after 10 seconds or so goes off line and fails to respond to any further requests.

Possible cause:- The Modbus registers in the camera are “input registers “ and are accessed by function code 04(3x). If you are using function code 03(4x) “holding registers” then the above symptom will occur.

To check use a software Modbus slave (Modsim or similar package)  then connect to the slave and look at it’s communication screen where it will show the data been received and the data sent back. The data been received is the one we are interested in and it will look similar to:-

mb-code                                                                                               

 

 

The one in red the function is the one of interest if it is 03 then change it in your application to function code 04 and the problem should be solved.

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