S7-SoftPLC:Differences between S7-SoftPLC and Hardware-PLC

Differences between S7-SoftPLC and a Hardware-PLC

In contrast to a conventional hardware-based control S7-SoftPLC does not have its own hardware. It always has to be integrated in an existing computer system with a Windows^® operating system.

Since S7-SoftPLC runs within a Windows^® operating system, other Windows^® applications such as EXCEL^® or ACCESS^® can access PLC-operands directly and fast without hardware wiring.

In contrast to a hardware-PLC the size of S7-SoftPLC 416 load memory can be changed flexibly (up to the maximum available memory size of the PC).

Differences between S7-SoftPLC 315 and S7-SoftPLC 416

The difference between S7-SoftPLC 315 and S7-SoftPLC 416 is a different number of flags, timers and counters according to the hardware-PLC.

The differences comply to the differences between the Siemens hardware PLC 315 and 416. The load memory of S7-SoftPLC 315 ist limited to 256 kByte, while the load memory of S7-SoftPLC 416 can be configured freely.

Non available features in S7-SoftPLC

Since there are physical differences between a hardware-PLC and a Windows computer, it is not possible to implement every feature of the CPU S7-315 resp. CPU S7-416 in S7-SoftPLC. However, existing programs should be executable on S7-SoftPLC with small changes.

The following organisation blocks are not supported:

• OB 60: multiple processor alarm
• OB 40 – OB 47: processor alarm 0 - 7

Time OBs are not terminated by Windows^®, which means those OBs are not allowed to have long cycle times(<1ms).

Furthermore SFBs and SFCs, that do not make sense on a PC platform, are not implemented. There is the possibility to extend S7-SoftPLC with user defined SFC's written in C++.

Diagnostic buffer

In addition to normal diagnostic buffer entries, which are recorded within the diagnostic buffer while starting or in case of programming errors, area transgressions or missing modules, there are additional entries.

Those are created by the hardware-drivers of S7-SoftPLC and give exact informations about the cause of an eventually occurred problem. Before contacting our support, please save an extract of the diagnostic buffer by using the programming unit. Doing so, an eventual problem can be located easily.

Starting S7-SoftPLC as service

In order to prevent accesses of non privileged users, PLC can be started as service. For this purpose S7-SoftPLC must be enlisted in the service list. Therefore open the command line and go to the installation folder of S7-SoftPLC.

Enter the following command in the command line interface:

C:\SoftSPS>plc416.exe –Service

An error message must not appear. S7-SoftPLC is now enlisted in the service list. Via "Control panel - Management - Services" the service "CPUS7" can now be found in the list. The start up can be set to "automatic", so that S7-SoftPLC starts without user logged in on the computer. It is also possible, that user accounts with limited rights can use S7-SoftPLC.

Delete S7-SoftPLC from the "Control panel - Management - Services", so that it can be executed as normal application

C:\SoftSPS>plc416.exe –RegServer

NOTE: ADMINISTRATIVE RIGHTS ARE REQUIRED

NOTE: IF THE DRIVER TWINCAT-IO IS USED WITH THE SOFT-PLC RUNNING AS SERVICE, THE INFORMATION PROVIDED [[../Configuration/TCDepend.htm|HERE]] SHOULD BE NOTED.

UPS operation

Most UPS programs provide the possibility to have certain operations executed before shutting down the PC. In most cases programs or batch files will be executed before the shut-down can be configured.

If the application "PlcStop.exe"(in the S7-SoftPLC installation directory) is configured here, the PLC saves the program and S7-SoftPLC is closed correctly thereafter.

Unauthorised accesses

With regard to unauthorized access to the computer, it is self-evident that S7-SoftPLC can not provide any security mechanisms.

Appropriate actions, customized to the application, have to be taken by the user.