The present invention provides a data processing apparatus and method for accessing memory. The data processing apparatus has a secure domain and a non-secure domain, in the secure domain the data processing apparatus having access to secure data which is not accessible in the non-secure domain. The data processing apparatus comprises a device coupled via a device bus with the memory, the device being operable, when an item of data in the memory is required by the device, to issue onto the device bus a memory access request pertaining to either the secure domain or the non-secure domain. The memory is operable to store data required by the device, and contains secure memory for storing secure data and non-secure memory for storing non-secure data. In accordance with the invention, the memory access request as issued by the device includes a domain signal identifying whether the memory access request pertains to either the secure domain or the non-secure domain. The presence of this domain signal issued as part of the memory access request enables checking to be performed to ensure that secure data within the secure memory is not accessed by the device when the memory access request pertains to the non-secure domain.