How to start with programming

[John]

I'm about to buy a PLC, exactly this:  SlimLine LogicLab IEC61131-3 Compact Ethernet CPU + PLC book in practice.

For now I have downloaded LogicLab version 2.5.0 and I am trying with simple programs (like a start-stop) to see if I can make it "work". For now by reading some forum posts and manuals I was able to simulate my circuit. But there are some things that I can't understand (it definitely depends on me…). I state that I worked with Siemens PLC even with an S5 so you can imagine how many years ago ... Having said that, my questions are:

When I declare a variable, for example an input, I can choose whether the address is: Automatic, or manually. If I choose the automatic address, when I simulate how do I know which address I find the interested entrance?

Always if I declare a variable, for example an output, I have to uncheck it from Automatic and choose as Position Output and the address. But if I only buy the CPU without I / O modules how do I do?

The last question always in the variable address window I can also check Memory. What does it mean ?

Enough with the questions for now, I hope you have time (and patience ...) to answer me, or can I find these answers in the book?

[Sergio Bertana]

In the forum you will find examples of programs that work with the simulator (See topical, topical, topical) and in the topics I have reported you will find useful information on the use of SimuLab which is the simulation environment of LogicLab. Even if the answers to some of your questions are already in these topics, let's see the answers.

Usually the variables on the state type Auto, for debugging I use the watch window in LogicLab or the SimuLab panels, simply by dragging the variable inside the window or panel. The variables are allocated by defining the address only for the real I / O or for the variables that must be reached from an external system, operator panel (See topical) or SCADA that are allocated in the DB100 (See topical).

The I / O of the CPU module are also allocated to them in the process image, they must be declared as Data block 255. So we will have% IX255.0 for input 0 and then below, and QX255.0 for output 0 and then below (See topical).

The Memory check is just to allocate the variables that must be accessible from Modbus, at the moment the only accessible memory is the Data block (DB) 100.

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