SIMATIC S7-300 PLC S7-300 PLC is a modular system of small, medium performance to meet the requirements of the application. Various individual systems can be constituted between the different requirements of a broad portfolio of Siemens S7 PLC family of modules. Compared with the S7-200 PLC, S7-300 PLC modular structure, with high-speed (0.6 ~ 0.1μs) instruction computing speed; with floating-point operations more effectively to achieve a more complex arithmetic operations; with a standard user interface user-friendly software tools for all module parameter assignment; convenient HMI services have been integrated in the S7-300 operating system, interactive programming requirements greatly reduced. SIMATIC Human Machine Interface (HMI) to obtain data from the S7-300, S7-300 specified by the user to refresh the data transfer speed. S7-300 operating system automatically handles data transfer; CPU features intelligent diagnostic system continuously monitors the system is normal, error, and special event recording system (for example: Timeout, module replacement, etc.); Multi-level password protection can be allowing users to highly effective technology to protect its secrets, to prevent unauthorized copying and modification; S7-300 PLC has operating mode selector switch, operating mode selector switch as key as you can pull out when the key is removed, it can not change the operating mode, so you can delete or overwrite prevent illegal user program. With powerful communications capabilities, S7-300 PLC can be programmed to provide communication configuration software Step 7 user interface, which makes it very easy to configure, simple. S7-300 PLC with a variety of different communication interfaces, and to connect the AS-I bus interface and industrial Ethernet bus system through a variety of communication processors; communications processor is used to connect a serial point to point communication system; Multi-Point Interface (MPI) integrated in the CPU, for simultaneous connection programmer, PC machine, HMI systems and other SIMATIC S7 / M7 / C7 and other automated control systems.