FFT 8.0, sink_ready de-asserted

Hi,

I am trying to test the functionality of FFT version 8.0. The device family that I am using is Cyclone II. Below is the parameter of the FFT:

Transform Length: 64 points

Data Precision: 8 bits

Twiddle Precision: 8 bits

I/O Data Flow: Streaming

Structure: 4 Mults/2Adders

Implement Multipliers in: DSP Blocks/Logic Cells

Twiddle ROM Distribution 100% M4K

As for the FFT input, I wrote a FSM code for it. My input looks fine, sink_sop, sink_eop and sink_valid are where it is suppose to be. However sink_ready was asserted at the beginning, one clock cycle before sink_valid and sink_sop were asserted. Then sink_ready was de-asserted half way before sink_eop (before 64 data ends). As a result, source_error shows “11”; meaning that EOP is asserted before 64 valid samples are accepted.

Since I am using streaming architecture, I thought this architecture allows continuous processing of input data and outputs a continuous complex data stream. So that means the sink_ready was suppose to be asserted all the time isn’t it? Unlike in buffered burst and burst architecture, sink_ready signal will be de-asserted when FIFO is filled. So why for streaming architecture in my case, the sink_ready can be de-asserted causing it unable to accept data? Does anyone know this answer?