Step7 - Read some bit from Word in Interface area

[Gambrinus]

I wouldn't be happy with that, temp marker bytes went out with S5.
It does not matter that the user is new, he should be taught the correct way, this forum would help anyone who does not understand indirect addressing.

I think using of indirect addressing is useful only when another way is not effective. Reasons? In first, many people know ladder only. Plant electrician with basic S7 knowledge can understand something in LAD program but he will be panic if he try to understand STL indirect. Simple problem - and you instead of sleeping must to go to PC. Indirect cann't be converted to LAD. Second, if you want to make your alghoritms portable, you must avoid indirect. For example, if I use MW40 and M40.0 in Siemens, I can use similar %MW40 and %MW40:X0 in Schneider. Conversion will be easy.

 

[PeterW]

I think using of indirect addressing is useful only when another way is not effective. Reasons? In first, many people know ladder only. Plant electrician with basic S7 knowledge can understand something in LAD program but he will be panic if he try to understand STL indirect. Simple problem - and you instead of sleeping must to go to PC. Indirect cann't be converted to LAD. Second, if you want to make your alghoritms portable, you must avoid indirect. For example, if I use MW40 and M40.0 in Siemens, I can use similar %MW40 and %MW40:X0 in Schneider. Conversion will be easy.

I disagree with both points really.

1. Plant electricians. I don't believe are as stupid as some make out. In the case of this example, even if they don't understand indirect code, a simple description of what it is doing would be suffice.

The code they would be more interested in would be the code using the individual bits once the indirect move was complete, not the indirect move itself.

2. One of the worse examples of software you can come across is software thats attempted to be ported from one PLC type to another.

All the different manufacturers have their strong points, trying to write code that easily ports from one to the other would end up not using any of them.

How do you port your exampe to Control Logix that has no flags as such.

Its better to write to the same specification and to each PLC's strengths.

 

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Im was trying it, it is easy and understandable, thanks.
....and functional !!!

To reference bits of a variable declared as a word use indirect addressing as follows. If you use the hardcoded L address, this may change if you add another variable in the future.

	 LAR1 P##TempWord
	 A	 [AR1,P#0.0]
	 A	 [AR1,P#0.3]
	 =	 M	 10.2