N7 Integer Files Micrologix

[Sherlock4me]

This will be too simple for you programmers. I am relearning programming skills for Rockwell software. I've got the basic instructions relearned after 10 years away...For now I have a Micrologix 1000, because that's the trainer I have at the moment. I have a few manuals but have yet to understand how N7 integer files are used as the Source B in say an EQU comparison instruction. Are we using a 16 digit binary word to compare with say the ACC bit of a T4 timer, so if the ACC gets to 25 or 60 or whatever, How does that compare in any way to a 16 bit binary word? Or are we not using binary in N7 files? Or are we turning the 16 bit binary word into a base 10 decimal number like 101 binary = 5?
It may be asking a lot for you to come down to my level. Perhaps someone may have suggested reading for me? Thanks so Much!!

 

[bernie_carlton]

The N7 file contents, like all other data files, is ultimately a collection of bits. The 'N' files are typically DISPLAYED as an integer. The 'B' files are typically DISPLAYED as individual bits. Though either can be displayed in the format of the other. In the lower right of a data file display note the 'Radix' box. Try changing that to view the data in different ways.

 

[jkerekes]

The N in the N7 file mean that it's an 16 bit integer file. It can hold integer values from -32768 to 32767. Normally you would of course store a single integer value in it. But you could just address one bit, i.e N7:0/1. You wouldn't normally do this. A Binary file such as B3, is also made up of 16 bit words. But here, they are usually addressed to the bit level such as b3:1/2. But for some purposes, the whole word can be addressed as B3:0 for example.

People use integer file in comparsions when the value may change depending on some other logic. Or the number may be entered via an HMI. Did this explain at least some of your questions?

 

[DamianInRochester]

N7 files are just a collection of integers. An integer is just a collection of bits. Whether you want to treat them as binary (base 2) or base 10 or base 16 is entirely a matter of perspective. The plc doesn't distinguish this. Only thing to keep in mind is if the MSB is to be interpreted a a signed bit or not.

 

[Eric Nelson]

There's a decent explanation in this YouTube video...

www.youtube.com/watch?v=ezeibwRNEg0



-Eric

 

[Sherlock4me]

Yes, It's helped. Thanks for the relpy!

 

[bernie_carlton]

By the way, don't apologise

It may be asking a lot for you to come down to my level.

We were all at your 'level' and it's good for us to review our basic understanding now and then. You'll soon be helping others.

 

[Linwo5]

Hello I need to use a hmi to change the preset value of a counter. I need a high limit of 25 and a lower limit of five. My hmi is already setup with the keypad. How do I use the N7 file with the limit test. I know I need to use the mov function. I'm having trouble addressing the code correctly. Thanks for the help.

 

[Lancie1]

Hello I need to use a hmi to change the preset value of a counter.

You could use something similar to the attached picture.

 

[bernie_carlton]

If the HMI has the ability on entry to display and enforce entry limits it is wise to use that IN ADDITION to the limit check in the ladder program. The presence of the limits would then be more apparent to the operator.