The age of the values an Opto 22 controller currently has for I/O points. Opto 22 controllers do not constantly scan I/O points. Instead, they scan only when necessary, based on control logic. When a controller reads I/O points, the value is time-stamped. If the data is too old, the controller must read the I/O point again before reporting. The freshness value and scan rates may be configurable.