The procedure 3964 (R) protocol controls data transfer via point-to-point connection between a local station and a communication partner. The procedure 3964 (R) includes the bit transfer layer (layer 1 of the ISO-OSI reference model) and the security layer (layer 2).
This security layer is available in the form of a control character. This control character checks the complete and error-free data transfer from the communication partner.
In the case of a connection via the procedure 3964 (R), the two communication partners must be configured with different priorities.
||The SEND function available for the system concerned in each case transfers a data area from a data block. This data area is defined by the data block number, the initial address and the length of the data to be transferred.|
||The RECEIVE function available for the system concerned in each case transfers received data areas from a data puffer into a target area. The target area is specified in the local station by a data block and the initial address of the data. The length of the data received is output after successful completion of the function.|
Advantages of the protocol:
- Can be used well with third-party systems.
- Suitable only for medium data volumes (<= 4096 bytes)
- Data transfer acknowledged by the communication partner
- High data security (hamming distance 3)
Disadvantages of the protocol:
- RS 485 cannot be used as bus medium
- Requires coordinated calls of send and receive functions
|Data area per job
||Up to 4096 bytes per message|
||Layer 2 of the ISO-OSI reference model|
|Number of possible connections per CP
||1 per interface (point-to-point)|
- General information on communication via SIMATIC S7 and a detailed description of the procedure 3964 (R) are available in Entry ID: 20982954.
- The difference between procedure 3964 and procedure 3964 (R) lies in the transfer of block check characters. Block check characters are transferred in procedure 3964 (R)
RK 512, Point-to-point, Serial connection, Third-party system