Description:
The computer link RK 512 controls controls data transfer via a bidirectional point-to-point connection between the local controller and a communication partner.
Here, the RK 512 protocol uses the transport layer known from the ISO-OSI reference model, layer 4. This provides a very high level of transfer security. Services used with RK 512 are acknowledged.

Protocol services:
 

Service	Description
PUT	In the case of a SEND/PUT message, the local station sends a command message with user data to the communication partner which in turn answers with a response message.
GET	In the case of a GET message, the local station sends a command message without user data and the communication partner answers with a response message with user data.

Advantages of the protocol:

• Can be used well with third-party systems.
• Suitable only for medium data volumes (<= 1024 bytes)
• Acknowledged data transfer
• Possible to read/write separately definable data areas

Disadvantages of the protocol:

• Not very good performance due among other things to use of procedure 3964R
• RS 485 cannot be used as bus medium

Quantity framework:
 

Parameters	Value range
Data area per job	Up to 1024 bytes per message (128 bytes per segment)
Logical interface	Layer 4 of the ISO-OSI reference model (technically speaking, the connection works on layer 7)
Number of possible connections per CP	1 per interface (point-to-point)

Note:
General information on communication via SIMATIC S7 and a detailed description of the RK 512 protocol are available in Entry ID: 20982954.

Keywords:
RK 512, Point-to-point, Serial connection, Third-party system