Available options included serial and Ethernet communications, digital input and output cards, analog signal processing boards, counter cards, and other specialized interface and function modules. Some systems provided redundant CPU operation for ultra-high-reliability control, as used in pharmaceutical manufacturing, for example.Įach chassis consisted of a power supply, and a backplane with slots for the addition of various option boards. Within each chassis style, several CPUs were available, with varying speed, memory, and capabilities. The higher the number (except for the 101U), the more sophisticated and more expensive the system was. Siemens has developed four product lines to date: For example, the Simatic 505 could handle floating point quantities and trigonometric functions. More complex inputs, outputs, and calculations were also supported as the Simatic line developed. “Low” signal: Temperature is within expected limitsīased on this input, and other factors, the program on the Simatic device might send a binary output signal to the same machine with the following meanings:.“High” signal: Temperature exceeded an operating limit.

For example, a binary input going from a thermometer on a machine to a Simatic device might have the following meanings: The programs on the Simatic devices respond in real time to inputs from sensors on the controlled machines, and send output signals to actuators on the machines that directing their subsequent operation.ĭepending on the device and its connection modules, signals may be a simple binary value ('high' or 'low') or more complex. Microprocessors were introduced in 1973, allowing programs similar to those on general-purpose digital computers to be stored and used for machine control. Simatic devices have input and output modules to connect with controlled machines. Early Simatic devices were transistor-based, intended to replace relays attached and customized to a specific machine. Siemens Simatic S7-300 PLC CPU with three I/O modules attachedĪs with other programmable logic controllers, Simatic devices are intended to separate the control of a machine from the machine's direct operation, in a more lightweight and versatile manner than controls hard-wired for a specific machine.

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