Siemens SIMATIC S7 System Manual page 533

Network 27: Go to the "Idle" state in all situations.
Network 28: State "Disconnect"...
Initiate a disconnect.
Network 29: Initiate the disconnect with the ConnID by calling the DISCONNECT instruction
with Req = TRUE.
Network 30: If Done is TRUE, this means that the disconnect is complete (probably will
never happen), so go try to reconnect.
If Busy is TRUE (this would be normal), go to the "Disconnect Wait" state.
If Error is TRUE, check the reason, and you may need to change state if there is a
connection issue.
Network 31: State "Disconnect Wait"...
Wait in this state for the disconnect operation to complete.
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
9.4 Open user communication library
Libraries
533