The system memory management unit (SMMU) provides protection services of slaves and address translation for I/O masters to identify more than its actual addressing capability. In absence of memory isolation, I/O devices can corrupt system memory. The SMMU provides device isolation to prevent DMA attacks. To offer isolation and memory protection, it restricts device access for DMA-capable I/O to a pre-assigned physical space. The SMMU consists of the translation control unit (TCU) and multiple translation buffer units (TBUs). The protection functions are described in System Protection Units. The translation functions are described in SMMU Architecture.