Data Memory

In a real PLC you distinguish mainly between four different areas of the data memory. At the beginning of each machining cycle the inputs are set to the value which the connected sensor gives. The CPU reads the inputs and specifies by the program the state of the outputs.

The connected actuators are operated by the outputs at the end of the scan. The markers and data blocks are used to save provisional results and parameter.

Naturally we have taken over this structure, in contrast to a real PLC the division into inputs, outputs, marker and data blocks in TrySim has only got a symbolical character: You can operate actuators with inputs, e.g., and influence the state of markers by sensors. If your program shall run on a real PLC in future you will not make use of these possibilities, of course, but while testing they are of great use. Suppose, your machine stacks boxes and the controller shall save how many boxes are at a specific position. Anywhere in your program is a mistake and the number is not correct occasionally. With TrySim you just take a digital display, connect it to the data word with the number of boxes and put it directly below the stack. Now you can see at once whether the number is not correct, so that you can encircle the mistake quickly.

See also:

PLC

Naming the Inputs, Outputs and Markers

Naming the Data in Data Blocks

Instance Data Blocks