Output image

I am hoping I am using the correct terminology on this so here goes. I have been experimenting with out RSLogix5 test bench in the shop and trying different things. I noticed while looking at different logic from other plcs' on site that they are using input/output imaging.

If I am seeing it correctly the input word 0-16 will generate a decimal value based on the binary inputs. The program then uses this value to activate the outputs. I was just wondering if doing it this way is a for that lack of a better term more processor friendly.

In the past I have just used what ever input was available to the plc did what ever I had to do ie TON/TOF/etc. then activated what ever output was not used at the time.

Being part of the lumber industy makes it hard to get proper training on plcs' as they are not spending a whole lot of money on anything so its just trial and error on the test bench.

Anyway short story long. Is an image type technique more processor friendly and a cleaner more accepted way to program.

If I am seeing it correctly the input word 0-16 will generate a decimal value based on the binary inputs. The program then uses this value to activate the outputs.

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I am not quite sure what you are referring to. A guess would be that you are talking about a program that uses a Sequencer Output instruction, where the Sequencer instruction controls an entire "word" (16 bits) of discrete outputs.

If so, that is only one type of instruction, and it is not appropriate for very many situations.

Most processors use an Input Image table. It is built-in and you have no choice about it, because it is part of the way the PLC operates. The Inputs are scanned and the values are copied into the Input Image Table. Then the processor evaluates (scans) each rung of logic, substituting the values in the image table for the input addresses. Then it evaluates the rung ouput based on those input images AND the logic contained in the rung.

Thanks for the response. Its getting clearer now.