Siemens SIMATIC S7-1500 Function Manual page 86

3. Select the required instruction, for example MB_CLIENT, from the "Instructions" task
card, "Communication" area, "Other", "MODBUS TCP" and drag it to a network of OB1.
4. Assign the parameters of the MB_CLIENT or MB_SERVER instruction. Observe the
following rules:
An IPv4 server address must be specified for each MB_CLIENT connection.
Each MB_CLIENT or MB_SERVER connection must use a unique instance DB with one
of the data structures TCON_IP_v4, TCON_QDN or TCON_Configured.
Each connection requires a unique connection ID. The connection ID and instance DB
belong together in pairs and must be unique for each connection.
Figure 6-9 MB_CLIENT
Figure 6-10 MB_SERVER
5. Download the hardware configuration and user program to the CPU.
Communication
Function Manual, 11/2019, A5E03735815-AH
Open User Communication
6.7 Setting up communication with Modbus TCP
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