SIMATIC S7-300 PLC S7-300是模块化小型PLC，能中等性能要求的应用。各种单独的模块之间可进行广泛组合构成不同要求的。与S7-200 PLC比较，S7-300 PLC采用模块化结构，具备高速（0.6~0.1μs）的指令运算速度；用浮点数运算比较有效地实现了更为复杂的算术运算；一个带用户接口的工具方便用户给所有模块进行参数赋值；方便的人机界面服务已经集成在S7-300操作内，人机对话的编程要求大大。SIMATIC人机界面（HMI）从S7-300中取得数据，S7-300按用户的刷新速度传送这些数据。S7-300操作自动地处理数据的传送；CPU的智能化的诊断连续监控的功能是否正常、记录错误和特殊事件（例如：超时，模块更换，等等）；多级口令保护可以使用户高度、有效地保护其技术机密，防止未经允许的和修改；S7-300 PLC设有操作选择开关，操作选择开关像钥匙一样可以，当钥匙时，就不能改变操作，这样就可防止或改写用户程序。具备强大的通信功能，S7-300 PLC可通过编程Step 7的用户界面提供通信组态功能，这使得组态非常容易、简单。S7-300 PLC具有多种不同的通信接口，并通过多种通信处理器来连接AS-I总线接口和工业以太网总线；串行通信处理器用来连接点到点的通信；多点接口（MPI）集成在CPU中，用于同时连接编程器、PC机、人机界面及其他SIMATIC S7/M7/C7等自动化控制。
SIMATIC S7-300 PLC S7-300 is a modular Small PLC, which can be used in applications with medium performance requirements. Various individual modules can be widely combined to form different requirements. Compared with S7-200 PLC, S7-300 PLC adopts modular structure and has high speed (0.6~0.1 μ s) Instruction operation speed; More complex arithmetic operations are effectively realized by floating-point operations; A tool with user interface is convenient for users to assign parameters to all modules; Convenient man-machine interface service has been integrated into S7-300 operation, and the programming requirements of man-machine dialogue are greatly increased. SIMATIC human machine interface (HMI) obtains data from S7-300, which transmits these data according to the user's refresh speed. S7-300 operation automatically processes the transmission of data; The intelligent diagnosis of CPU continuously monitors whether the function is normal, records errors and special events (such as timeout, module replacement, etc.); Multi level password protection enables users to highly and effectively protect their technical secrets and prevent unauthorized and modification; S7-300 PLC is equipped with an operation selection switch, which can be operated like a key. When the key is used, the operation cannot be changed, so as to prevent or rewrite the user program. With powerful communication function, S7-300 PLC can provide communication configuration function through programming the user interface of step 7, which makes the configuration very easy and simple. S7-300 PLC has a variety of different communication interfaces, and connects AS-I bus interface and industrial Ethernet bus through a variety of communication processors; The serial communication processor is used to connect point-to-point communication; Multipoint interface (MPI) is integrated in CPU, which is used to simultaneously connect programmer, PC, man-machine interface and other automation controls such as SIMATIC s7/m7/c7.