FIR IP configured for Interpolation

To be clear - does this allow you to move forward right now?  The functionality of "tready" is only a pass-through of the tready on the source side (input).  Per the documentation, it's not a function of the current status of the internal FIR.  So, you need to create your signaling to match the system behavior, which is what I articulated in the drawing.  If you are seeing bursts of data coming in, you might need to add a simple FIFO/buffer that pulls data out at the 1-in-80 and absorbs bursts on the write side (not to exceed a net rate of 1-in-80, of course).