Libraries 
  9.4 Open user communication library 
S7-200 SMART 
System Manual, V2.3, 07/2017, A5E03822230-AF 
541 
: Send the data back to the partner. 
 
: If Done is TRUE, the send is complete (probably never happen this quickly), so 
go to the "Receive" state on the next scan. 
If Busy is TRUE (this is the normal situation), go to the "Transmit Wait" state to wait for the 
transmit to finish. 
If Error is TRUE, check the reason, and you may need to change state if there is a 
connection issue. 
 
: State "Transmit Wait"... 
Wait in this state until the transmit is complete. 
 
: Call the TCP_SEND instruction with Req = FALSE to determine when the send 
is complete. Be sure to use the same send length and buffer pointer that you used to 
initialize the send request.