S7 Indirect Addressing

bmw_apprentice · Jul 5, 2007

Hey Guys,

Im sure this has been asked a million times on this forum but how exactly does indirect addressing work within Siemens S7. i have a basic idea of it but i want to clear that out and learn from scratch to save confusion.

not only how it works would be helpful though but where it could be used, thats the biggest problem i have at the moment; i understand stuff but i cant practically use it which isnt any use to anybody.

if there is any websites that explain it that would be helpful.

L D[AR2P#0.0] · Jul 5, 2007

Here's a simple example to start you off. The following function accepts a byte and bit address and a boolean to select between the I and Q area. The output of the function is the value of the I/O specified. I use this function for connecting an arbitrary I/O point to my machine horn so I can check it's state (when working on my own and I can't see my laptop or the i/o modules for example).

As has already been suggested, Berger's book will be a good reference.

Code:

FUNCTION FC 277 : VOID
TITLE =
VERSION : 0.1

VAR_INPUT
  iByteAddress : INT ; 
  iBitAddress : INT ; 
  bTrueForQFalseForI : BOOL ; 
END_VAR
VAR_OUTPUT
  bMonitoredBool : BOOL ; 
END_VAR
BEGIN
NETWORK
TITLE =monitor i/o specfied by parameters
	  L	 #iByteAddress; 
	  AW	W#16#FF; 
	  SLD   3; 
	  L	 #iBitAddress; 
	  AW	W#16#7; 
	  +D	; 
	  A	 #bTrueForQFalseForI; 
	  JC	qmon; 
	  LAR1  P#I 0.0; 
	  JU	sum; 
qmon: LAR1  P#Q 0.0; 
sum:  +AR1  ; 
	  A	  [AR1,P#0.0]; 
	  =	 #bMonitoredBool; 
END_FUNCTION

PeterW · Jul 5, 2007

Take a look at the help manual, in the appendix at the back is a description of data formats and quite good ones of the POINTER and ANY data formats.

Should help to understand the build of the addresses.

bmw_apprentice · Jul 6, 2007

cheers for that, ill give that a go and see how i get on. what is this book you speak of? where can i get it? is it online or can i buy it from amazon?

L D[AR2P#0.0] · Jul 6, 2007

google gives the following:-

http://www.amazon.co.uk/Automating-STEP-STL-SCL-Programmable/dp/3895782955

S7 Indirect Addressing

bmw_apprentice

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L D[AR2P#0.0]

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PeterW

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bmw_apprentice

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L D[AR2P#0.0]

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