XIO — Examine If Open

dataBit

/

Passes power along the rung when the referenced bit is 0. Equivalent to a normally-closed contact.

Operands

Name	Type
dataBit	BOOL

How It Works

If dataBit is 0, power passes through. If 1, power is blocked.

Example

XIO(Fault)OTE(Ready)

Ready is energized while Fault is 0.

Practice

Try XIO in the Lamp Inverted exercise — light a lamp while a button is released.

Looking for NOT?

There is no NOT contact in Ladder Logic. For inverting a bit on a rung, XIO is the NOT — it passes power when the bit is off. (Do not confuse it with the Move/Logical NOT block, which complements a whole DINT word rather than a single bit.)

Common Mistakes

• Expecting a NOT or ! symbol on a contact — use XIO instead.

Related

• XIC — the non-inverted counterpart
• Bit instructions overview
• Logical instructions — the NOT block, for inverting a whole DINT word