H2C MM Engine - 1.0 English

Versal ACAP DMA and Bridge Subsystem for PCI Express Product Guide (PG344)

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1.0 English

The H2C MM Engine moves data from the host memory to card memory through the H2C AXI-MM interface. The engine generates reads on PCIe, splitting descriptors into multiple read requests based on the MRRS and the requirement that PCIe reads do not cross 4 KB boundaries. Once completion data for a read request is received, an AXI write is generated on the H2C AXI-MM interface. For source and destination addresses that are not aligned, the hardware will shift the data and split writes on AXI-MM to prevent 4 KB boundary crossing. Each completed descriptor is checked to determine whether a writeback and/or interrupt is required.

For Internal mode, the descriptor engine delivers memory mapped descriptors straight to the H2C MM engine. The user logic can also inject the descriptor into the H2C descriptor bypass interface to move data from host to card memory. This gives the ability to do interesting things such as mixing control and DMA commands in the same queue. Control information can be sent to a control processor indicating the completion of DMA operation.