FFT IP Core: User Guide

ID 683374
Date 11/06/2017
Document Table of Contents Component Specific Signals

The component specific signals.
Table 11.  Component Specific Signals 
Signal Name Direction Size Description
fftpts_in Input log2(maximum number of points) The number of points in this FFT frame. If you do not specify this value, the FFT can not be a variable length. The default behavior is for the FFT to have fixed length of maximum points. Only sampled at SOP. Always drive fftpts_in even if you are not dynamically changing the block size. For a fixed implementation drive it to match the transform length in the parameter editor.
fftpts_out Output log2(maximum number of points) The number of points in this FFT frame synchronized to the Avalon-ST source interface. Variable streaming only.
inverse Input 1 Inverse FFT calculated if asserted. Only sampled at SOP.

Incorrect usage of the Avalon-ST interface protocol on the sink interface results in a error on source_error. Table 3–8 defines the behavior of the FFT when an incorrect Avalon-ST transfer is detected. If an error occurs, the behavior of the FFT is undefined and you must reset the FFT with reset_n.

Table 12.  Error Handling Behavior 
Error source_error Description
Missing SOP 01 Asserted when valid goes high, but there is no start of frame.
Missing EOP 10 Asserted if the FFT accepts N valid samples of an FFT frame, but there is no EOP signal.
Unexpected EOP 11 Asserted if EOP is asserted before N valid samples are accepted.