View source for 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<sup>®</sup> operating system.

Since ''S7-SoftPLC'' runs within a Windows<sup>®</sup> operating system, other Windows<sup>®</sup> applications such as EXCEL<sup>®</sup> or ACCESS<sup>®</sup> 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<sup>®</sup>, which means those OBs are not allowed to have long cycle times(&lt;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:

<code>C:\SoftSPS&gt;plc416.exe –Service</code>

An error message must not appear. ''S7-SoftPLC'' is now enlisted in the service list. Via &quot;Control panel - Management - Services&quot; the service &quot;CPUS7&quot; can now be found in the list. The start up can be set to &quot;automatic&quot;, 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 &quot;Control panel - Management - Services&quot;, so that it can be executed as normal application

<code>C:\SoftSPS&gt;plc416.exe –RegServer</code>

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 &quot;PlcStop.exe&quot;(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.