MC92307 Datasheet, PDF (3/10 Pages) Motorola, Inc – 2K - Samples FFT-Processor

External Interfaces
If NOMUX is set to H the real and imaginary part of one
sample is transferred in parallel using the DINR and
DOUTR lines for the real part and the DIN and DOUT
lines for the imaginary part. Consequently the transfer
rate is divided by 2 compared to the muxed mode at the
cost of more interconnection lines. Therefore this mode
is intended mainly for use with external devices that op-
erate on lower rates.
REVRSB
Table 2. Output resolution selection
RES[1:0]
00
01
10
11
DOUT[11:0]
[0, 0, d₉, d₈, ... ,d₀, ]
[0, d₁₀, d₉, d₈, ... ,d₀, ]
[d₁₁, d₁₀, d₉, d₈, ... ,d₀, ]
Don’t care
To achieve the output of the frequency domain data in
natural order an internal bit reversal is done in the out-
put reorder buffer. This bit reversal can be switched off
e.g. to allow the combination of 4 MC92307 devices to-
OFDM Device -> FFT Device
The figures below illustrate the input of the time domain
gether with an external final radix-4 butterfly stage to do
an 8K-FFT.
RES[1:0]
data into the FFT device and the output of the calculat-
ed frequency domain data after the completion of the
FFT. The samples belonging to the real part are denot-
ed by ...r (real), the imaginary samples are marked with
These two lines support the selection of the wordlength
at the FFT output:
...q (quadrature). Figure 2 applies for the Multiplexed
mode, Figure 3 is valid for the Non-multiplexed mode.
formation ^CLK
In _DIN
inary ^FFTSTART
Prelim ^DOUT
X0r X0q X1r X1q ^...
Xir
... _{Xq X(i+1)r X(i+1)q}
... _{Z(N-i)r Z(N-i)q Z(N-i+1)rZ(N-i+1)q}
Z0r
Z0q
Z1r
Z1q ^...
SYMSYNC
Figure 2. FFT Data I/O for the Multiplexed Mode
MC92307_DS - 8/12/97
MOTOROLA
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