Testing a Channel with Requests
Original instructions
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Sending a Request
You can test a communication channel from the debugging screen through different requests.. The following procedure allows a request, other than those provided by the command buttons, to be sent to a designated station. In this example, the request sent is used to read 10 words (from %MW1 to %MW10).
Step
Action
1
Select the address of the station to be interrogated with the help of the field Station.
2
Click the Input Request button. The following window appears.
The data sent in this example is coded on 6 bytes.
3
Input the function code (coded in hexadecimal on one byte), corresponding to the request that you want to send.
For this example the read request code is 16#36.
4
Input the data to be sent by coding all the data in hexadecimal. The data is sent non-stop without any time intervals between them. When the data is coded on one word, the most significant and least significant bytes are reversed.
For this example the data is as follows:
  • 16#68: on one byte, defines the segment (internal data)
  • 16#07: on one byte, defines the object type (words)
  • 16#0100: on one byte, defines the first word to read
  • 16#0A00: on one byte, defines the number of words to read
5
Click the Send button. The response appears in the Receive Response window.
The response from the example has data on 21 bytes:
  • 16#07: corresponds to object type (words)
  • 16#00C2: corresponds to the value of the first word (the most significant and least significant bytes are reversed, its value is 16#C200)
  • ...