Iso_Connect Instruction - Siemens SIMATIC S7 System Manual

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9.4 Open user communication library

This is an example usage of the TCP_CONNECT instruction:

ISO_CONNECT instruction

The ISO_CONNECT instruction creates a connection to another device using the ISO-on-

TCP protocol. This protocol uses RFC1006 in addition to the TCP protocol to better delineate

messages. The advantage of ISO-on-TCP is that every sent message results in a different

received message. The ISO-on-TCP protocol never combines multiple received messages

into one message, as can happen with TCP protocol. The ISO-on-TCP protocol uses TSAPs

(Transport Services Access Point) to route the message in the device instead of ports.

ISO_CONNECT Req, Active,

ConnID, IPaddr1, IPaddr2,

IPaddr3, IPaddr4, RemTsap,

LocTsap, Done, Busy, Er-

The connect operation is asynchronous and can take several scans to complete. The

instruction sets the Busy output while the connect operation is pending. When the CPU

completes the operation, the instruction sets either the Done or Error output. If there is an

error, the Status output contains the error code.

The ISO_CONNECT creates an ISO-on-TCP communications

connection from the CPU to a communication partner.

System Manual, V2.3, 07/2017, A5E03822230-AF

S7-200 SMART

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