Honored Contributor
Honored ContributorThe "control signal of DEMUX" is the Avalon-ST "channel" signal: the DEMUX is simply routing the incoming Avalon-ST packet (your ethernet frame) to the Avalon-ST interface that is indicated by the 'channel' signal.
In the UDP offload example, the "UDP port to channel mapper" is the component which creates the 'channel' information, as it is not something normally part of the TSE output. In this example, it is basically a small lookup on the UDP packet 'port' and if a match is found in the control registers, it sends the packet with the corresponding channel number; otherwise it sends it to channel "4" which will end up with the NIOS software via the SGDMA. This is on or around line 513 of udp_port_to_channel_mapper.v For getting started, I would recommend to continue to use the existing mapper component, but only connect your new component and the NIOS SGDMA ports to the DEMUX. Or, you can copy & modify the original mapper and alter it to only support (2) channels.
