Example: Legacy Mb_Client 1: Multiple Requests With Common Tcp Connection - Siemens SIMATIC S7-1200 System Manual

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Example: Legacy MB_CLIENT 1: Multiple requests with common TCP connection

Multiple Modbus client requests can be sent over the same connection. To accomplish this,

use the same instance DB, connection ID, and port number.

Only 1 client can be active at any given time. Once a client completes its execution, the next

client begins execution. Your program is responsible for the order of execution.

The example shows both clients writing to the same memory area. Also, a returned error is

captured which is optional.

Network 1: Modbus function 1 - Read 16 output image bits

Network 2: Modbus function 2 - Read 32 input image bits

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Communication processor and Modbus TCP

13.8 Legacy Modbus TCP communication