A system comprises a central processing unit (10), an interconnection bus (1), and a plurality of functional modules (11-15, 21) corresponding to distinct power domains and able to communicate with each other and/or with the central processing unit via the bus. At least one of the power domains, and is configured to be substituted for a slave functional module (21) of the power domain when the power to the power domain is turned off by the central processing unit. It signals an error in response to any request of a transaction that is in progress between the slave functional module and a master functional module at the moment the power is turned off.