ADSP-214xx SHARC Processor Hardware Reference
6-21
FFT/FIR/IIR Hardware Modules
Effect Latency
The total effect latency is a combination of the write effect latency (core
access) plus the peripheral effect latency (peripheral specific).
Write Effect Latency
For details on write effect latency, see the
SHARC Processor Programming
Reference
.
FFT Accelerator Effect Latency
After the FFT registers are configured the effect latency is 1.5
PCLK
cycles
minimum and 2
PCLK
cycles maximum. Writes to the
PMCTL1
register have
an effect latency of two
PCLK
cycles. Wait for at least four
CCLK
cycles after
selecting an accelerator before accessing any of its registers.
Programming Model
There are two separate programming models, one for a FFT that fits in the
accelerator’s internal memory (N = 256 points or less) and one for a FFT
that is larger than the accelerator’s internal memory (N = 512 points or
more). In both models, is assumed that the accelerator starts in idle mode.
N <= 256, No Repeat
For details on the storage format of the coefficients see
1. Configure the
ACCSEL
bits in the
PMCTL1
register to select the FFT
accelerator.
2. Program the
FFTCTL2
register with:
VDIM
= N/16
LOG2VDIM
= Log2(N)
HDIM
= 0
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Содержание SHARC ADSP-214 Series
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