Siemens programming

I have a Siemens S7 program to write, Whilst im not new to programming im new to the siemens brand. I have completed the example engine project and read the documentation but am still unsure on the best way to go, i would like your views.
Am i right in thinking
if for example i need to write a section in the program where i need to create a unconditional 1 second on, 1 second off pulse that is moved into a bit for other devices to look at (possible that it may be a block i would use more than once)
Then
I would enter the i/o into the symbol list and Create a FB that contains 2 timers addressed from the symbol list and then pulsing a output that is addressd from the FB variable table
next
i would create a instance DB for that FB and then put an instruction to call the FB from OB1,assigning the puse output a symbol list address

or should i just put it all in OB1 to begin with?

What pitfalls are related to using the FB,FC blocks?

appoligys if it sounds a too simple question

Andy

Do you have access to the plc and/or plcsim ?

I realise that you're actually looking for the answer to a broader question, but specifically to the pulse generation part, you can define a Marker Byte (in the CPU properties) which will give you eight Bits pulsing in frequencies from 0.5 Hz to 10 Hz, so you don't need to set up your own Timers to do this.

You must be using S7-300 or higher version
You have to start with ob1 and if you want to write programs in functions (FC) or function blocks (FB) simply call these blocks in OB1. It is better if you start writing with Functions (FC) first before Function blocks (FB) that requires a Data block (DB) associate with it.
Go through the programming manuals you can write your programs in ladder, FBD or STL

Best Regards

Palitha

Andy,
What is your program controling?

I have developed a lot of siemens programs and this might give you some ideas on program structure common bit's FC'c & FB's.


M.W (www.ac-sys.co.uk)