One of the key functions of the Ethernet
AVB Endpoint is the configurable bandwidth allocation for the AV user data. Because this
bandwidth is managed over time, this is done using credits which are gained when non-AV data
is sent and lost, when AV data is sent with a positive or zero balance of credits enabling
the AV path. When no data is present at the AV input, any credits available are removed thus
preventing bursty AV traffic from getting an artificially high bandwidth. The tx_axis_av_tvalid indicates that data is available, but at the
end of a frame, if another frame is available, the tx_axis_av_tvalid should remain asserted and the first byte of the new frame should
be presented. This is shown in the previous figure. If tx_axis_av_tvalid is dropped between frames then any positive credit balance is lost
and a negative balance remains, which results in a lower overall bandwidth allowance for the
AV path.