Bits And Data Table

Could some one expline to me about the binary bits and how they work with the plc logic thank you

Look at this site for downloads to get info. If you are a student,
you should be able to find what you need.
http://www.ab.com/manuals/abs/

Take a look at this sheet it may help you.

You know that we (humans) use a base 10 math system. Computers (which a plc is) cannot use that, they can use base 8 (octal), base 16 (hexadecimal) and base 2 (binary). Base 2 (binary) consists of 2 digits 0 (zero) and 1 (one).

BIT is actually a shortened term that means Binary digIT, the smallest unit of information. A bit can only be a 0 or 1.

With PLC's bits are grouped into word files which are 16 bits in length. These word files are what creates your Data Tables...Binary, Integer, Input, Output etc.

Using an AB as a reference if you view the Binary File for B3:0 then you would see from right to left 0 to 15 which represents the bits, next in line will be B3:1 with 16 bits to use.

What can be confusing is that some Data Files seem to use 2 word files, there are simple reasons for that. Using AB again lets look at an INPUT file which seems to hold 32 bits ie 2 word files that is because in some cases 32 bit cards are used. SO if you are using a rack style system and have a 32 bit input card in slot 1 it makes sense to allow the Input numbers to follow suit Input 1/0 to 1/32.

THis is a very basic overview and others may post more eloquent explanations. Note not all plc's do things like AB but the basis is the same 16 bits create a word or memory file. I used AB references because I think that is what you are using to learn by.