FFT IP Core: User Guide

ID 683374
Date 11/06/2017
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3.6.2. FFT IP Core Avalon-ST Signals

Table 10.  Avalon-ST Signals
Signal Name Direction Avalon-ST Type Size Description
clk Input clk 1 Clock signal that clocks all internal FFT engine components.
reset_n Input reset_n 1 Active-low asynchronous reset signal.This signal can be asserted asynchronously, but must remain asserted at least one clk clock cycle and must be deasserted synchronously with clk.
sink_eop Input endofpacket 1 Indicates the end of the incoming FFT frame.
sink_error Input error 2 Indicates an error has occurred in an upstream module, because of an illegal usage of the Avalon-ST protocol. The following errors are defined:
  • 00 = no error
  • 01 = missing start of packet (SOP)
  • 10 = missing end of packet (EOP)
  • 11 = unexpected EOP

    If this signal is not used in upstream modules, set to zero.

sink_imag Input data data precision width Imaginary input data, which represents a signed number of data precision bits.
sink_ready Output ready 1 Asserted by the FFT engine when it can accept data. It is not mandatory to provide data to the FFT during ready cycles.
sink_real Input data data precision width Real input data, which represents a signed number of data precision bits.
sink_sop Input startofpacket 1 Indicates the start of the incoming FFT frame.
sink_valid Input valid 1 Asserted when data on the data bus is valid. When sink_valid and sink_ready are asserted, a data transfer takes place..
sink_data Input data Variable

In Qsys systems, this Avalon-ST-compliant data bus includes all the Avalon-ST input data signals from MSB to LSB:

  • sink_real
  • sink_imag
  • fftpts_in
  • inverse
source_eop Output endofpacket 1 Marks the end of the outgoing FFT frame. Only valid when source_valid is asserted.
source_error Output error 2 Indicates an error has occurred either in an upstream module or within the FFT module (logical OR of sink_error with errors generated in the FFT).
source_exp Output data 6 Streaming, burst, and buffered burst FFTs only. Signed block exponent: Accounts for scaling of internal signal values during FFT computation.
source_imag Output data (data precision width + growth) Imaginary output data. For burst, buffered burst, streaming, and variable streaming floating point FFTs, the output data width is equal to the input data width. For variable streaming fixed point FFTs, the size of the output data is dependent on the number of stages defined for the FFT and is 2 bits per radix 22 stage.
source_ready Input ready 1 Asserted by the downstream module if it is able to accept data.
source_real Output data (data precision width + growth) Real output data. For burst, buffered burst, streaming, and variable streaming floating point FFTs, the output data width is equal to the input data width. For variable streaming fixed point FFTs, the size of the output data is dependent on the number of stages defined for the FFT and is 2 bits per radix 22 stage. Variable streaming fixed point FFT only. Growth is log2(N)+1.
source_sop Output startofpacket 1 Marks the start of the outgoing FFT frame. Only valid when source_valid is asserted.
source_valid Output valid 1 Asserted by the FFT when there is valid data to output.
source_data Output data Variable

In Qsys systems, this Avalon-ST-compliant data bus includes all the Avalon-ST output data signals from MSB to LSB:

  • source_real
  • source_imag
  • fftpts_out