SIEMENS SIMATIC S7-300 Automation System



  • The modular mini PLC system for the low and mid-performance ranges
  • With comprehensive range of modules for optimum adaptation to the automation task
  • Flexible use through simple implementation of distributed structures and versatile networking
  • User-friendly handling and uncomplicated design without a fan
  • Can be expanded without problems when the tasks increase
  • Powerful thanks to a range of integrated functions

Application areas of the SIMATIC S7-300 include:

  • Special machinery,
  • Textile machinery,
  • Packaging machinery,
  • General mechanical equipment manufacture,
  • Controller building,
  • Machine tool manufacture,
  • Installation systems,
  • Electrical/electronics industry and the skilled trades.
Siemens S7 300 Design

The S7-300 automation system is modular in design. It has a comprehensive range of modules that can be combined individually.

A system includes the following:

  • A CPU:
    Different CPUs are available for different performance ranges, including CPUs with integral inputs/outputs and the corresponding functions, as well as CPUs with integral PROFIBUS DP, PROFINET and point-to-point interfaces.
  • Signal modules (SMs) for digital and analog inputs/outputs.
  • Communications processors (CPs) for bus connection and point-to-point connections.
  • Function modules (FMs) for high-speed counting, positioning (open-loop/closed-loop) and PID control.

The S7-300 has different communication interfaces:

  • Communications processors for connecting to the bus systems AS-Interface, PROFIBUS and PROFINET/Industrial Ethernet.
  • Communications processors for point-to-point connections.
  • Multipoint interface (MPI ), integrated into the CPU;
    the low-cost solution for simultaneous connection of PGs/PCs, HMI systems and other SIMATIC S7/C7 automation systems.

A host of features support users in programming, commissioning and servicing the S7-300.

  • High-speed instruction processing:
    Instruction execution times from 4 ns open up completely new application options in the low-end and mid performance range.
  • Floating-point arithmetic:
    With floating-point arithmetic, even complex arithmetic functions can be used effectively.
  • User-friendly parameter assignment:
    There is only one single software tool with a uniform operator interface for parameterizing all modules. This saves on induction and training overhead.
  • Human machine interfacing (HMI):
    User-friendly HMI services are already integrated into the operating system of the S7-300. Costly programming of these functions is no longer necessary: The SIMATIC HMI system requests process data from the SIMATIC S7-300 — the S7-300 transfers this data at the desired update times. The operating system of the SIMATIC S7-300 handles the transfer autonomously. And all with uniform symbols and database.
  • Diagnostics functions:
    The intelligent diagnostics system of the CPUs continuously checks the functionality of the system and registers faults and specific system events (e.g. time errors, module failure, etc.). The events are stored in a ring buffer and time-stamped for future troubleshooting.

Image result for Siemens S7 300 Design

Siemens S7 300 Diagnostics


Digital input/output modules

Diagnostics message

Possible fault cause

No sensor supply

  • Sensor supply overload
  • Short-circuit of the sensor supply to M

No external auxiliary voltage

  • No supply voltage L+ of the module

No internal auxiliary voltage

  • No supply voltage L+ of the module
  • Internal module fuse defective

Fuse blown

  • Internal module fuse defective

Incorrect parameters in module

  • Incorrect parameters transferred to module

Time monitoring addressed (watchdog)

  • Periodically high electromagnetic interference
  • Module defective

EPROM fault

  • Periodically high electromagnetic interference
  • Module defective

RAM fault

  • Periodically high electromagnetic interference
  • Module defective

Hardware interrupt lost

  • Hardware interrupts come faster than the CPU can process them

Analog input modules

Diagnostics message

Possible fault cause

No external load voltage

  • No load voltage L+ of the module

Configuring/parameterization errors

  • Incorrect parameters transferred to module

Common mode error

  • Difference in potential UCM between the inputs (M-) and reference potential of the measuring circuit (MANA) too high


  • Resistance of sensor circuit too high
  • Interruption of the line between the module and the sensor
  • Channel not switched (open)

Measuring range low limit violated

  • Input value lower than the underrange, fault possibly caused by
    • Measuring range 4 to 20 mA, 1 to 5 V:
      sensor connected with reverse polarity;
      wrong measuring range selected
    • Other measuring ranges:
      wrong measuring range selected

Measuring range high limit violated

  • Input value exceeds overrange