The RTO instruction requires a separate _____ instruction to reset its accumulated value.

The correct answer is associated with the specific operation required to reset the accumulated value of the RTO (Retentive Timer On) instruction. The RTO instruction keeps track of the elapsed time as long as the timer is energized. Once the timing operation is complete, if you want to restart the timing sequence or clear the accumulated time, a separate instruction is needed.

The RES (Reset) instruction is utilized for this purpose. When employed, it effectively sets the accumulated value back to zero, allowing the RTO timer to start accumulating time again from that point onward. This is crucial in applications where ongoing tracking of time intervals is needed, enabling precise control and functionality in the system.

The other options do not perform the same function. The SET instruction is typically used to start certain operations, while CLR (Clear) may not specifically be designed for resetting timers, and INIT (Initialize) suggests a setup process rather than resetting a timer's value. Thus, RES is specifically tailored for the task of resetting the accumulated value of the RTO instruction, making it the correct choice.