Altera FFT MegaCore Function User Manual
Page 35
Figure 3-11: FFT Buffered Burst Data Flow Output Flow Control
clk
source_realt
source_imag
source_exp
source_ready
master_source_valid
source_sop
source_eop
EXP0
Xr[0] Xr[1] Xr[2] Xr[3] Xr[4] Xr[5] Xr[6] Xr[7] Xr[8] Xr[9] Xr[10]
Xi[0] Xi[1] Xi[2] Xi[3] Xi[4] Xi[5] Xi[6] Xi[7] Xi[8] Xi[9] Xi[10]
Signals
source_sop
and
source_eop
indicate the start-of-packet and end-of-packet for the output block
data respectively.
Note: You must assert the
sink_valid
signal for
source_valid
to be asserted (and a valid data output).
You must leave
sink_valid
signal asserted at the end of data transfers to extract the final frames of
data from the FFT.
RT** For information about enabling the buffered burst FFT, refer to
.
1. Deassert the system reset.
2. Asserts
sink_valid
to indicate to the FFT function that valid data is available for input. A successful
data transfer occurs when both the
sink_valid
and the
sink_ready
are asserted.
3. Load the first complex data sample into the FFT function and simultaneously asserts
sink_sop
to
indicate the start of the input block.
4. On the next clock cycle,
sink_sop
is deasserted and you must load the following N – 1 complex input
data samples in natural order.
5. On the last complex data sample,
assert sink_eop
.
6. When you load the input block, the FFT function begins computing the transform on the stored input
block. Hold the
sink_ready
signal high as you can transfer the first few samples of the subsequent
frame into the small FIFO at the input. If this FIFO buffer is filled, the FFT deasserts the
sink_ready
signal. It is not mandatory to transfer samples during
sink_ready
cycles.
3-12
Enabling the Buffered Burst FFT
UG-FFT
2014.12.15
Altera Corporation
FFT IP Core Functional Description