modbus RTU connection problem


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I don't know if the problem is modbus problem or Serial port issue

I wrote project using Quick - Device Configuration to config the modbus RTU connection to 4 controllers and most of the time its work fine but somtime when I open the project there is no communication and the project not trying to connect to throw the serial port (the project is not on save mode ) .

I thought its because the Port is lock or something like that so I restart the computer but I have the same problem.

I change to safe mode and check the port with Hyper Terminal and its work fine .

The only way to solved this problem was to delete the modbus serial connection that config using Quick - Device Configuration , and open new serial port with the same name and its work fine .

1.why its happen ?

2. what is better using the Quick - Device Configuration or using Sequences ?

3.can it happen because I am using the Silver Key licence ?

10x for the help

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1. There are a number of ways this could happen. Did you see any message about the comm port being in use or unable to init the comm port?

2. you have to use quick-device config to at least setup the comms. A better question is Sequences or Channels? and the answer to that depends on how much control you need. Usually Channels is easiest, but offers less control (and error handling). You can use a combination by using the Channel.ReadGroup() function.

3. no. The hardware key doesn't affect anything but licensing.

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