An integrated circuit comprises a write bus coupled to a register for storing control data. A storage unit is arranged to store reference signature data encoding a reference collective state of the register. First logic circuitry generates actual signature data encoding the actual collective state of the register. Second logic circuitry is coupled to the storage unit, receives the actual signature data and compares the actual signature data with the reference signature data. The second logic circuitry comprises an alert output to provide an alert signal in response to the comparison identifying a difference between the actual signature data and the reference signature data, thereby ensuring detection of a data integrity error in respect of the register. An alert inhibitor comprises a control input and is responsive to the control input and arranged to inhibit selectively onward propagation of the alert signal from the alert output.