Concept Programming

J

Thread Starter

Jon Stewart

In Concept is there any way to use "pointers" or "Indirect Addressing", ie. use the number in one register to point to another?
 
I know in AB plc5 and slc500 you can use stuff like N7:[N12:0] in instructions. I believe you could make things even more confusing and have two levels of indirection like N[N12:0]:[N12:1]

BUT... the people that follow in your footsteps will curse you when they see what you've done. Please consider liberal use of 'cut & paste'/'search & replace' instead.
 
1. You can use GET_4X, GET_3X, PUT_4X functions. Also you can make EFB blocks (with EFB Toolkit) for finding 4x or 3x address for variable.
2. You can make EFB blocks (with EFB Toolkit) for find point of variable, read or write variable for point.
 
Yes, there are many ocasions, applying "pointer" is the only way for improving the efficiency.

Let's say, there are many analog input points in the system, all of them change in a slow rate. In your application, you need to use those input data for a very complicated calculation process.

Since those data do not change for every cycle, if we do the math. on every data together, it slow down the system. Using a pointer, we can do the math on each data one by one.

A simple math:
1000 analog input points
Calculation process on a single data takes 1ms
Do the math on every input point on every cycle, cycle time: >1 sec/cycle
(If the analog inputs do not change on every cycle, we did not use the resource efficiently)

Using Pointer:
1000 analog input points
Calculation process on a single data takes 1ms
Do the math on a single input point on every cycle, cycle time: >1 ms/cycle

Conclusion: Without applying pointer, the ladder won't work, because of the cycle time is too long, With the help from pointer, the problem solved.

Pointer also can be used to build:
Dynamic Data Logging System,
Multi-dimension matrix operation system,
Receipe Retrieving System
so on...

Author is a PLC program Expert, and instructor of PLC Programming in College
 
B

Bob Peterson

Indexing and indirection are wonderful tools if you limit yourself to using them in well thought out and well documented ways. They can become very confusing if not documented. Having said that, they are great for creating recipes and such.

Bob Peterson
 
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