Siemens SIMATIC S7 System Manual page 472

Libraries
9.1 Library types (Siemens and user-defined)
Open user communication
Open User Communication (OUC) provides a mechanism for your program to transmit and
receive messages over an Ethernet network. You can select the Ethernet protocol used as
the transport mechanism: UDP, TCP, or ISO-on-TCP
You can find these instructions in the Libraries folder of the Instructions folder in the project
tree (Page 111). When you put an OUC library instruction in your program,
STEP 7-Micro/WIN SMART automatically puts one or more associated subroutines in your
project.
Note
The CPU models CPU CR20s, CPU CR30s, CPU CR40s, and CPU CR60s have no
Ethernet port and do not support any functions related to the use of Ethernet
communications.
USS protocol
The USS protocol library supports Siemens drives. The STEP 7-Micro/WIN SMART USS
instruction libraries make controlling drives easier by including preconfigured subroutines
and interrupt routines that are specifically designed for using the USS protocol to
communicate with the drive. With the USS instructions, you can control the physical drive
and the read/write drive parameters.
You can find these instructions in the Libraries folder of the Instructions folder in the project
tree (Page 111). When you put a USS library instruction in your program,
STEP 7-Micro/WIN SMART automatically puts one or more associated subroutines in your
project
Security: Protecting networks against physical access and possible reads and writes of
PLC data
Communication through Modbus RTU, Open User Communication, and USS Protocol
library instructions have no security features. If an attacker can physically access your
networks through one of these forms of communication, the attacker can possibly read and
write PLC data. Unauthorized access to PLC data can result in death or severe personal
injury.
You must protect these forms of communication by limiting physical access. For security
information and recommendations, refer to the following document: Operational Guidelines
for Industrial Security
security/Documents/operational_guidelines_industrial_security_en.pdf)
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WARNING
(http://www.industry.siemens.com/topics/global/en/industrial-
System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART