The PLC Ladder program is based on whether or not there is power flow through the logic rung. When there is power flow, the RLO, Result of Logical Operation, is positive, or ON. At the left-hand ladder rail, there is always power flow; therefore the RLO at the rail may be considered as ON. When there is no power flow, the RLO is negative, or OFF.
RLO to Bit takes the status of the RLO and stores it in a register bit according to the desired offset.
The rung in the following figure is shown in Online Test mode, showing the power flow in red. The Compare operation (MI1>MI2) in the rung is true. Therefore power flows through the rung, and the RLO is positive (ON). The state of the RLO is stored in MI 3, at an offset of 2 bits, in the third bit of MI 3. The bit turns ON, and MI 3 contains 4.
In the following figure, the Compare operation is false. Therefore power does not flow through the rung, and the RLO is negative (OFF). The state of the RLO is stored in MI 3, at an offset of 2 bits, in the third bit of MI 3. The bit turns OFF, and MI 3 contains 0.
Note that the maximum number of bits in the vector is 255, 16 MIs or 8 double registers.