The SoftPLC PLC S5-943 / PLC S5-945 executes a program in the same manner as a hardware PLC. The advantage of executing a PLC program program this way is, that the PLC status can be displayed in real time. Since the SoftPLC behaves like a original SIMATIC® PLC, the programming tools S5 for Windows® and STEP®5 can be used. Online connections can be established serial, via Ethernet and directly in the same PC. The program of a S5-PLC can be transferred to the SoftPLC PLC S5-943 / PLC S5-945.

Operating systems
To meet the demands of our customers and provide flexibility, a variety of hardware and software platforms are available that are supported by the software PLC. The S5 version can be installed on systems using Windows NT 4.x/2000/XP.

SoftPLC I/Os
The SoftPLC can access standard I/O boards as well as numerous intelligent hardware boards available to control bus systems widely used in the industry (PROFIBUS DP, INTERBUS, DeviceNet, CAN-Bus). Drivers have been developed to connect bus system interface boards with the SoftPLC.

SoftPLC on a Single Processor System
In a single processor system, the software PLC simultaneously shares the CPU time with other applications to be executed. The CPU time allocation is freely scaleable. For instance fifty percent (50%) of the CPU time (time slice) is assigned to the software PLC and the other 50% is used by the other applications. The software PLC is called within a preset timeframe.

SoftPLC on a Dual Processor System
In a Windows NT/2000/XP environment with a dual processor system, one CPU is exclusively reserved for the software PLC. The PLC cycle time depends on the execution time of the OB1. If OB1 has a short execution time, the number of cycles per time period is high.

SoftPLC on an additional processor board
There are Coprocessor boards available, running the SoftPLC. These Coprocessor boards can be plugged into the motherboard of the PC. The SoftPLC is running completely independent from the PC hardware. The additional processor board may be powered with its own power supply. Such a set up has the advantage of being independent of a PC failure that would impact the SoftPLC. Well-known manufacturers offer processor boards with integrated bus interfaces (InterBus, PROFIBUS, Can Bus, ASi Bus, DeciveNet) as a complete PLC solution.

Monitoring, Operating, and Controlling simultaneously, from one PC
The SoftPLC integrated in a PC allows process monitoring, operation, and control from one hardware unit. The use of the SoftPLC is especially useful, if a PC for data collection, process visualization, programming, or any other reason needs to be used anyway. Such a solution eliminates the need for a hardware PLC and the corresponding communication processor

Integrated Watchdog Function
Intelligent up-to-date Bus Control Boards today have integrated watchdog functions. These watchdog functions guarantee that the inputs and outputs of the SoftPLC, in case of a hardware failure of the PC, are handled in the same way as a hardware PLC CPU. If the PC fails, all the outputs of the Bus System are resetted.

Scalability
There are two versions of the S5 compatible SoftPLC. The major difference between them is the size of the PLC program memory. The PLC S5-943 has 48kB of program memory and the PLC S5-945 has 720kB of program memory. The execution time of the software PLC, of course will depend on the execution time of the PCs processor. Both versions have an integrated PID algorithm. Internally, the PID algorithm uses floating point operations to increase accuracy. To be compatible with a Siemens CPU, the interface of the PID algorithm matches the Siemens interface.