Indirect adressing

victorherr

Member
Join Date
Jul 2003
Posts
13
Im getting a little more involved in programming using AB Contrologix, I can not understand what is indirect adressing or how to use it, is there someone that can give me some simple examples on pointer and indirect adressing, please as simple as possible, that way i can build on that.
Im simply clueless on this.
 
Indirect addressing has been covered on this forum a million times. Very basically, indirect addressing in the PLC word is using one tag (memory location) to point to another memory location. In ControlLogix, since it's a tag based controller, indirect addressing is used with arrays. For example lets say we have a ControlLogix array called Array. It has ten DINT elements. So in the tag organizer it will how up as Array[10]. The elements are Array[0] to Array[9]. For indirect addressing, instead of supplying a fixed element such as Array[2], we could do something like Array[index]. index would be another tag, either a DINT or INT. Now whatever value index is, that's what element would be referenced i.e, if index is 5, the it would be Array[5]. Yout have to be careful not to have the value of index go out of the range of the Array or a major fault will occur.
 

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