Communicate with partner thru ASCII protocol via RS485

 I have S7-1200 with CM1243-5, so CPU1200 is Profibus DP master. Then I have IM 151-1 Basic with 2_SI module 4DF01, installed in ET200S rack. In HW Config this SI module gets hardware_ID 286. And now I want to communicate with partner thru ASCII protocol via RS485 line using this module. I use such call

"SEND_PTP_DB"(REQ:="DB61". SendReq, //it is true while call

                      "PORT":=286,

                      BUFFER:="DB61".SendBuffer, //it is string

                      LENGTH:="DB61".LengthOfRequest, //it is length of string upper

                      DONE=>"DB61".SendDone,

                      ERROR=>"DB61".SendError,

                      STATUS=>"DB61".SendStatus);

in status i get 7000 (block idle).

Why idle? Can somebody say me what I am doing wrong?

Is it possible at all to be CPU1200 as master in free ASCII communication?

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Split from Receive data from ET200S SI with S7 1200.