A method is provided for controlling processing of target program code on a host data processing apparatus to simulate processing of the target program code on a target data processing apparatus. In response to a target memory access instruction of the target program code specifying a target address within a simulated address space having a larger size than a host address space supported by a memory management unit of the host data processing apparatus, an address space resizing table is looked up to map the target address to a transformed address within said host address space, and information is generated for triggering a memory access based on translation of the transformed address by the memory management unit of the host data processing apparatus.