Real Outputs Only), Decimation By 2 - Motorola DSP56305 User Manual

12.5.5.3 Mode 0 (Complex FIR Filter Generating Real Outputs Only),
Decimation by 2
The following equation is implemented:
Set Up
DSP
Initialization
Processing
MOTOROLA
N 1 –
∑
FR n ( ) ( HR i ( ) DR n i –
=
i = 0
• Load Filter Count Register (FCNT) with (number of coefficient
values – 1)
• Choose operation mode (FOM[1:0], FDCM=0, 0, 1) and enable
FCOP (FEN = 1)
Core initializes coefficients in FCM in reverse order, while
•
imaginary coefficients are first negated, by executing
#filter_count writes to FCIR
• Core or DMA initializes data in FDM in direct order by
executing #filter_count writes to FDIR
Whenever FDIR is empty (FDIBE = 1), the FCOP triggers
•
core or the DMA to transfer two or four new data words
(one or two complex pairs) to the FDM via FDIR
• Compute F(n) and store result in FDOR
• FCOP triggers core or DMA for output data transfer
• Get new data word
• FCOP increments data memory pointer
• Get new data word
• FCOP increments data memory pointer
DSP56305 User's Manual
⋅ ( ) ) ( HI i ( ) DI n i –
–
Filter Co-Processor
Operation Modes
⋅ ( ) )
12-21