ENO is a Boolean output for boxes in LAD and FBD. ENO allows you to connect boxes in series (horizontally) rather than in parallel (vertically). If the box has power flow at the EN input and the box executes without error, then the ENO output will pass power flow to the next element. In the event that an error is detected in the execution of the box, then power flow will be terminated at the box that generated the error.
ENO has the same status image as EN (EN=ENO), unless the operation does not execute correctly. For example, the DIV_I instruction provides ENO=0 for a divide by zero.
In STL there is no ENO output, but the STL instructions that correspond to the LAD and FBD instructions with ENO outputs do set a special ENO bit. This bit is accessible with the STL instruction AENO (AND ENO) and may be used to generate the same effect as the ENO bit of a box.