Bit labels?

I'm a reasonably novice programmer. I am somewhat comfortable with Koyos offerings. I have had some training with Koyo's equipment at a local technical institute as part of an associates degree program. I have programmed some in-house built equipment at the plant where I work. Nothing huge though, no math functions and no data storage/retrieval functions. Primarily just timing and logic or logical sequence functions based on discrete inputs. 26 discrete inputs and 27 discrete outputs.

 I:0/1                  ?     

--] [------------------( )--





   ?                  O:0/1             

--] [------------------( )--

I am particularly interested in futhering my knowledge/comfort level with AB's line because of its prevalence in the OEM, and more specifically, the automotive manufacturing world. I thank you in advance for your patience.

In the above ladder with a Koyo unit, I would use the address C0 (through Cxxx depending on the available range) to allow I:0/1 to turn on O:0/1.

I bought the LogixPro Simulation training software for the RSLogix software and have gathered some basic information through the tutorials. I know that I could use the following in place of the ? to make the statements true:

S:0/0
B3:0/0
N7:0/0

and there are probably more. I ran these through the simulator and was able to make them work.

My question is: Why? Could someone give me an example of an application or a "rule of thumb" as to why I would use one over another or what the difference is?

Thank you.

The files you mentioned:
S:0/0
B3:0/0
N7:0/0
represent different types of files
S:0/0 is a bit in the status files
B3:0/0 is binary or bit file..used similar to C (control) in AD
N7:0/0 is an integer file at the bit level

NOTE: the 0 represents the word level of that type file the second 0 represents the bit level of that word file.

S: Status files offer a multitude of things...example would be time/date, which could be used to trigger something
B3 as stated is the binary/bit/control file, these are used internally the same as the control bits in the AD
N7 is an integer file..its possible that you have a tank with a full point and that is used to stop filling...simple example but maybe it explains some aspect of it. Its also possible to use bit(s) to condition rungs.

My .02

Yes, you could use Sx:y/z, maybe. Status file words and bits are not always writable - some are, some aren't. Besides, 'S' elements are more oriented for controlling how the processor behaves while it executes your ladder program or getting some information from the processor which will impact your program.

'B'inary bits are just that, bits. They correspond roughly to the 'C' type in Koyo land. These are generally used whenever you need an internal coil, a latch (though any data table bit can be given a latch instruction), or maybe a ONS (one shot). Because of this usage, the bit patterns in a binary file word would normally appear to randomly change as various parts of the ladder turn bits on and off. The point is, the individual bits don't necessarily have any relation to their neighbors.

'N' words are generally used to hold a signed number, like -577, or 1283. In this type the bits are interpreted to have the 1, 2, 4, 8, ... place value relationship encountered in binarily represented numbers. Although you can do it, it's not usually seen that isolated bits within N words are examined or manipulated.

An exception might be when you want to know the sign of a number. You could do a compare (greater than or equal) of the number with zero. If it is, the logic does one thing, if not, another. You could also just check the sign bit of the number:

 N7:50/15           B3/27

---| |---------------(L)----

In this example B3/27 will latch if the value in N7:50 is negative.

The integer type is also the PLC-5's native mode of arithmetic manipulation. If you reference two N type words and add them the result will be the one expected (excepting math errors like overflow or divide by zero). If you, say, ADD an integer and a BCD type though, your results may or may not have any meaning.

Is this any help?

I equate AB's N: files to the V-memory in AD's world.

Yes, that helps a bunch

Thanks for the info.

Great explanation. I working my way through the LogixPro exercises and that wasn't directly covered though it may be covered later and I'm jumping ahead.

Has anyone else tried the LogixPro simulations? Any thoughts on it usefulness?

I used Logix pro when I first started and it helped me out alot. It seems people don't like you to learn/play on their machines. Go figure.

It doesn't act exactly like RSLogix, but it's very close. It's great for beginners because the basic stuff is just like AB's software.