ModBus+Socket read PLC , The first read must have timed out ,Why?

[sxbug]

Using MODBUS demo（V9.57）, it is found that when using TCP connection to read PLC, no matter whether the RTU or ASC connection is used at the beginning, the data will not be read and the  Timeout !!! will be displayed. After disconnecting, modify the mode, No matter what is changed(if it was ASC change to RTU, if it is RTU change to ASC), It can read PLC data after connecting again. No matter how you modify the mode in the future, It can read PLC data.

It is not a problem of disconnection/Connect. If you do not modify the mode value, no matter how you disconnect or connect, you will not be able to read it, and the display will be time out.



Please check. Thank you

[Roman Novgorodov]

Hello

Please check the problem in v9.58

Roman Novgorodov

[sxbug]

Hello
It has been checked in  v9.58 , and all the problems have been solved.
THANKS！！！
But there is one thing I don't understand: No matter what mode(ASC or RTU) is set, PLC can be read. What's the use of this setting(nrModbus.ASC)?
Thanks


     sxbug

[Roman Novgorodov]

Hello

Hmm... The ASCII and RTU modes are absolutely differ.
They provide different data formats (text and binary) and differ check sum (lrc and crc).
Maybe your PLC firmware can detect mode on the fly. I do't know :-(

Roman Novgorodov

[sxbug]

Hi

Thank you for your help. Let me test it again. Find out why.

    sxbug