A flight control computer (FCC) has an index calculation component (ICC) configured to compare a reasonableness of at least a first value of a variable and a second value of the variable. A method of operating a flight control computer (FCC) includes providing an index calculation component (ICC) configured to compare a reasonableness of at least a first value of a variable and a second value of the variable.

A flight control computer (FCC) has an index calculation component (ICC) configured to compare a reasonableness of at least a first value of a variable and a second value of the variable. A method of operating a flight control computer (FCC) includes providing an index calculation component (ICC) configured to compare a reasonableness of at least a first value of a variable and a second value of the variable.

A master device is provided which is coupled to a shared single line interrupt request (IRQ) bus and a control data bus. The master device group slave devices coupled to the shared single line IRQ bus into one or more groups, where each group is associated with a different IRQ signal. The master device then monitors the IRQ bus to ascertain when an IRQ signal is asserted by at least one slave device. The master device then identifies a group to with which the IRQ signal is associated. The slave devices for the identified group are then scanned or queried by the master device to ascertain which slave device asserted the IRQ signal on the IRQ bus. Each group uses a distinguishable IRQ signal to allow the master device to ascertain which group to query or scan.