Allen-Bradley program symbols for ladder logic

flashman

Member
Join Date
Mar 2004
Posts
8
My question is in regard to the XIO, XIC symbols for Allen-Bradley ladder logic programming.
Basically, When an input or output is on, is it shown by a N.O. set of contacts?
Then when it is off, it is shown by a N.C. set of contacts?
So, XIO=ON and XIC=OFF.
Not electrically, where N.C.= on and energized, and N.O.= off and de-energized?

-It’s been a while since I last programmed and I’d appreciate it if someone could advise me.

flashman
 
So, imaginarily speaking, the n.o. contact symbol means "on" or true and the n.c. contact symbol means "off" or false.
If I just think of it as a series of on/off conditions generating an output then I'll be OK. Otherwise, I may need a beer!

Thanks for the imaginary reality check!
 
XIC and XIO are "Allen Bradley speak" for NO and NC contacts. Nobody else uses that nomencalture. Others may disagree, but if you understand ladder diagram schematics stick with NO and NC and pull the symbol from the menu and you will be OK.
 
XIC, instruction, instruct the processor, input in the field (XIC = Examine if closed)) if so then get the ladder true.
XIO, Exaim if open if so then get the ladder true.
I remember this way.
 
XIC and XIO are "Allen Bradley speak"

Tom is right - only AB uses these terms. You'll probably see from some of the other recommended posts that this can cause a good deal of confusion.

Just remember that

XIC means: "true if a one is at that data table address"
XIO means: "true if a zero is at that data table address"

Marc
 
true or not true

Thanks for the picture!
I'm thinking of the input as being true enabling the output and not true to disable the output?
 
XIC examine if closed
XIO examine if open
refer to the state of an input or memory coil.
The reference above about Allen Bradley is correct, the definition was misleading.
If the field device (or memory coil on) provides a complete circuit to the PLC input a XIC bool command will cause the rung output to be true or active.
If the conditions of the input device are the same, a XIO bool command will cause the rung output to be false.

Bitmore
 
Last edited:

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