For maximum flexibility, flow control
logic can be disabled in the core (see MAC Configuration Registers) and alternatively
implemented in the client logic connected to the core. Any type of the error free control
frame is then passed through the core with the rx_axis_tuser
signal de-asserted. In this way, the frame is passed to the client for interpretation. It is
the responsibility of the client to drop this control frame and to act on it by ceasing
transmission of the appropriate priorities through the core, if applicable.