The AXI Direct Memory Access (AXI DMA) IP core provides high-bandwidth direct memory access between the AXI4 memory mapped and AXI4-Stream IP interfaces. Its optional scatter gather capabilities also offload data movement tasks from the Central Processing Unit (CPU) in processor-based systems. Initialization, status, and management registers are accessed through an AXI4-Lite slave interface. This Figure illustrates the functional composition of the core.
Primary high-speed DMA data movement between system memory and stream target is through the AXI4 Read Master to AXI4 memory-mapped to stream (MM2S) Master, and AXI stream to memory-mapped (S2MM) Slave to AXI4 Write Master. AXI DMA also enables up to 16 multiple channels of data movement on both MM2S and S2MM paths in scatter/gather mode.
The MM2S channel and S2MM channel operate independently. The AXI DMA provides 4 KB address boundary protection (when configured in non Micro DMA), automatic burst mapping, as well as providing the ability to queue multiple transfer requests using nearly the full bandwidth capabilities of the AXI4-Stream buses. Furthermore, the AXI DMA provides byte-level data realignment allowing memory reads and writes starting at any byte offset location.
The MM2S channel supports an AXI Control stream for sending user application data to the target IP. For the S2MM channel, an AXI Status stream is provided for receiving user application data from the target IP.
The optional Scatter/Gather Engine fetches and updates buffer descriptors from system memory through the AXI4 Scatter Gather Read/Write Master interface.