These are normal input signals which do not latch nor do they create an interrupt within the controller. Data from high speed inputs is serviced using the normal input update methods, at the end of the scan.

As the scan time of an average application program is in the ms range, the normal I/O service at the end of the scan will not benefit from those fast inputs. However together with interrupt processing where all inputs on an HLI module are read immediately after the interrupt input has been triggered, it is essential to use this inputs for all time critical signals associated with the interrupt routine.