need help on plc addressing

I try to read several explanations regarding PLC addressing on the internet but it seems that I am not fully satisfied. I need a brief and concise explanation on " direct, indirect, indexe addressing" I would appreciate if you can paste examples and applications on both.

I hope that somebody can share me a light on this..

Thanks and Godbless.

Danpreps

On the Internet?

Yeah Terry, you know, http://www.plctalk.net/qanda/N7:0

"...PLC addressing on the internet..."

I tend to use PLC Addressing on my PLC... not on the Internet.

In Alice in Wonderland...

When Alice pressed the point that Humpty-Dumpty's explanation about such-n-such was non-sensical, H-D responded by saying...

The words I use mean exactly what I intend them to mean... nothing more, nothing less.

A direct address is like a street address. Its always the same place. 2342 Washington Lane is a direct address. It can mean only one place.

An indirect address doesn't tell you the exact address number, but it tell you how many houses to go on the street to find it. This number can be changed.
Its the sixth house on Washington Lane or
Its the tenth house on Washington Lane

An indexed address would be when the house location is described in relation to a nearby known address. This can also be changed.
Its the second house after 2305 Washington Lane or
Its the fifth house after 2305 Wahsington Lane.

Alaric, Thank you so much for sharing your ideas, This is a big help. Terry Woods, I am asking for explanation regarding PLC addressing, nothing more, nothing less.... " IF YOU CANNOT SAY SOMETHING NICE, YOU BETTER SAY NOTHING AT ALL "

danpreps said:

" IF YOU CANNOT SAY SOMETHING NICE, YOU BETTER SAY NOTHING AT ALL "

Click to expand...

You missed the point. Your question was not clearly defined and phrased improperly.

A simple search of this forum would offer an abundance of topics that explains indirect or indexed addressing with examples.

As for direct addressing, if you dont understand that then you need to find another field to study.

Danpreps, I hoped that helped, but I admit I sniggered at the other posts. If you think about it your question was phrased to invite a good bit of ribbing. It was done in fun, not spite.

To elaborate more using the street address example,

B3:0/9 refers to only a single bit in memory. It cannot refer to any other.

B3:0/[N7:0] can refer to any bit in the word B3:0. If the number in N7:0 is a five, then it refers to the fifth bit, or B3:0/5. But dont go sticking a 19 in N7:0 - you'll indirect past the end of the word.

If the value in S:24 is 5 then #N7:3 is an indexed address that refers to the address five words after N7:3, or N7:8. If S:24 is -1 then its the address one word before N7:3, or N7:2.

You can combine indirect and indexed addresses, as in its the third house past the sixth house on Washington Lane, but if you are a beginner I recommend you avoid that until you have a grip on the fundamentals first.

Alaric,

Thats a great explaination! (the house thing).

Danpreps, Some manufactures call/refer to indirect addressing as "pointers" the pointer is the memory space that holds the address of the memory to access next. (like it Points to it).

So if you see the word "pointer" in a PLC manual, there you have it.

Geez, you big boys can be too tough sometimes

Guys, thank you so much for sharing your brilliant ideas, I learn a lot from you..

danpreps