The zoom selector for the ff table and scope

The zoom selector affects the time scale of both the feed forward table and scope acquisition, although differently.

The ff table outputs duplicate I, Q, −I, −Q sequences of each I/Q waypoint depending on the zoom. Its capacity is 1024 words, so it holds 512 I/Q pairs. At its fastest rate, the ff-table output duration is 51 μs. The zoom selector affects the output duration by setting the multiplicity of the output of the I, Q, −I, −Q sequence for each I/Q pair by the factor 2^zoom+1.

The scope span is also affected by the zoom, but in a different way due to the fact that it must acquire all quadrants by sampling at multiples of four clock periods ±1. The scope buffers also are 1024 words in capacity, so, at its highest rate (one sample per clock), the scope fills its buffer in 25 μs. This is the zoom = 0 rate. At higher zoom (zoom > 0), the scope function samples every 2^zoom+1+1 samples. Although the ff table output and scope acquisition never have the same duration, they asymptotically match at high zoom.