Siemens SIMATIC S7 System Manual page 416

Communication
8.4 Ethernet
To ensure that your CPU and HMI are communicating properly, follow the sequence of steps
in the table below:
Table 8- 1 Required steps in configuring communications between an HMI and a CPU
Step Task
1 Establishing the hardware communications connection
An Ethernet interface establishes the physical connection between an HMI and a CPU. Since Auto-Cross-Over
functionality is built into the CPU, you can use either a standard or crossover Ethernet cable for the interface.
An Ethernet switch is not required to connect an HMI and a CPU.
Refer to "Establishing the hardware communications connection" (Page 33) for more information.
2 If you have already created a project with a CPU, open your project in STEP 7-Micro/WIN SMART. If not, cre-
ate a project and insert a CPU In the project.
3 Configuring an IP address in your project
Use the same configuration process; however, you must configure IP addresses for the HMI and the CPU. You
must download the configuration for each CPU and HMI device.
Refer to "Configuring or changing an IP address for a CPU or device in your project" (Page 404) for more in-
formation.
Note
You can restrict communication writes to a specific range of V memory; this can affect HMI
communications. See "Configuring system security" (Page 143) for more information.
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System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART