A input_gmio or output_gmio object is used to make external
memory-mapped connections to or from the global memory. These connections are made
between an AI Engine graph
and the logical global memory ports of a hardware platform design. The platform can
be a base platform from AMD or a custom
platform that is exported from the Vivado tools
as a Xilinx support archive (XSA) package.
AI Engine-ML tools support mapping the input_gmio
or
output_gmio port to the tile DMA, one to one. It
does not support mapping multiple input_gmio/output_gmio ports to one
tile DMA channel. There is a limit on the number of input_gmio/output_gmio ports
supported for a given device. For example, the XCVE2802 device on the VEK280 board
has 12 AI Engine-ML to NoC master units (NMU) in
total. For each AI Engine-ML to NMU, it supports two
MM2S and two S2MM channels. So, there can be at most 24 AI Engine-ML GMIO inputs, and 24 AI Engine-ML GMIO outputs. Note that it can be further limited by the
existing hardware platform.
While developing data flow graph applications on top of an existing hardware platform, you need to know what global memory ports are exported by the underlying XSA and their functionality. In particular, any input or output ports exposed on the platform are recorded within the XSA and can be viewed as a logical architecture interface.