soft plc??

Is a soft plc simply a sofeware simulation that runs on a standard pc?? If so would there not be a lack of I/O on a standard pc??

No, a "soft PLC" is a PLC engine that works just as a hardware PLC.
To talk with the IO, there can be IO boards in the PC it self, or a communication card that talks to remote IO (Profibus, DeviceNet ..).

There is another type of software that "simulates" the PLC and its IO.
Its basically the same as the "soft PLC", but it just doesnt have any real IO. It is used for simulation of the PLC program during the development phase.

Hello!

It depends; sometimes the soft plc is just a software running on a computer, but it can also be a dedicated piece of hardware that's placed inside the computer like an expansion card (typically a PCI card, just using the computer as a "power supply") and running its own dedicated software.

To control IO's and communicate to the "world" it usually uses communication cards for profibus, can, softbus or ethernet or any other bus system (or vendor specific cards) to control external IO.
Usually there's no IO directly inside the computer, just controlled from the computer.

Regards
Borte

JesperMP was faster than me...

Borte