How can PLC input instructions be controlled by output instructions?

How can PLC input instructions be controlled by output instructions?

• A. Output instructions can be used as inputs for XIC and XIO; for example, a true OTE on one rung can activate an XIC on the next rung
• B. Input instructions can be controlled by output instructions but only if the OTE is the previous rung's tag
• C. Only timer tags can control input instructions
• D. Input instructions can only be controlled by other input instructions

Answer: (A)

In ladder logic, the state of outputs is stored in memory just like inputs, so an output can act as a condition for subsequent rungs. When an OTE energizes its coil, that coil’s tag becomes true. That true tag can be read by input instructions (XIC or XIO) on the next rung or any later rung, allowing the logic to flow based on whether the previous output is on or off. This lets you sequence actions: a rung turns something on, and the next rung uses that ON state to decide what happens next (XIC passes when the coil is true, XIO passes when the coil is false). Other choices aren’t correct because an output’s tag can control input instructions, not just a previous rung’s tag, and inputs can be controlled by outputs, not only by other inputs or by timers.

In ladder logic, the state of outputs is stored in memory just like inputs, so an output can act as a condition for subsequent rungs. When an OTE energizes its coil, that coil’s tag becomes true. That true tag can be read by input instructions (XIC or XIO) on the next rung or any later rung, allowing the logic to flow based on whether the previous output is on or off. This lets you sequence actions: a rung turns something on, and the next rung uses that ON state to decide what happens next (XIC passes when the coil is true, XIO passes when the coil is false).

Other choices aren’t correct because an output’s tag can control input instructions, not just a previous rung’s tag, and inputs can be controlled by outputs, not only by other inputs or by timers.