Abstract: An apparatus has a control domain comprising functional circuitry to perform logical operations when in an operational state. The functional circuitry comprises at least one output and a state of the output depends on the logical operations. Domain control circuitry controls the control domain to put the functional circuitry in one of the operational state and a non-operational state. Isolation circuitry isolates the functional circuitry within the apparatus by holding the state of the output at a predetermined value when the domain control circuitry puts the functional circuitry in the non-operational state. Self-test control circuitry causes the domain control circuitry to control the control domain to put the functional circuitry in the non-operational state and to cause a self-test procedure to be carried out with respect to the functional circuitry.

Abstract: Apparatuses and methods of controlling an apparatus are disclosed. An apparatus comprises a control domain comprising functional circuitry to perform logical operations when in an operational state, wherein the functional circuitry comprises at least one output and a state of the at least one output is dependent on the logical operations. Domain control circuitry controls the control domain to put the functional circuitry in one of the operational state and a non-operational state. Isolation circuitry isolates the functional circuitry within the apparatus by holding the state of the at least one output at a predetermined value when the domain control circuitry puts the functional circuitry in the non-operational state. Self-test control circuitry causes the domain control circuitry to control the control domain to put the functional circuitry in the non-operational state and to cause a self-test procedure to be carried out with respect to the functional circuitry.