Motorola DSP56000 Manual page 578

; All coefficients are divided by 2:
; w(n)/2=x(n)/2-ai1/2*w(n-1)-ai2/2*w(n-2)
; y(n)/2=w(n)/2+bi1/2*w(n-1)+bi2/2*w(n-2)
;
; X Memory Organization
;
;
;
;
; wN(n-1)
; wN(n-2)
; •
; •
; w1(n-1)
; R0 w1(n-2)
;
;*********************************************************************************************************************
; initialization
;*************************************
nsec equ
start equ
data equ
coef equ
input equ
output equ
igain equ
ori
move
move
move
move
move
opt
; filter loop: 4*nsec + 9
;*********************************************************************
movep
mpy
;
do
mac
macr
mac
mac
end_cell
rnd
movep
;****************************************************************************************
end
Figure B-5 Real Input FFT Based on Glenn Bergland Algorithm (Sheet 5 of 8)
B - 16
BENCHMARK PROGRAMS
Y Memory Organization
Data + 2*nsec - 1
Data R4
4
$40
0
0
$ffe0
$ffe1
0.5
#$08,mr ;set scaling mode
#data,r0 ;point to filter states
#coef,r4 ;point to filter coefficients
#2*nsec - 1,m0
#4*nsec - 1,m4
#igain,y1 ;y1=initial gain
cc
y:input,y0
y0,y1,a x:(r0) +,x0
#nsec,end_cell
-x0,y0,a x:(r0) -,x1
-x1,y0,a x1,x:(r0) +
x0,y0,a a,x:(r0)+
x1,y0,a x:(r0) +,x0
a
a,y:output
BENCHMARK PROGRAMS
b1N/2 Coef. + 4*nsec - 1
b2N/2
a1N/2
a2N/2
•
•
b11/2
b21/2
a11/2
a21/2 Coef.
;get sample
y:(r4)+,y0 ;x0=1st section w(n-2),y0=ai2/2
;do each section
y:(r4) +,y0 ;x1=w(n-1),y0=ai1/2
y:(r4) +,y0 ;push w(n-1) to w(n-2),y0=bi2/2
y:(r4) +,y0 ;push w(n) to w(n-1),y0=bi1/2
y:(r4) +,y0 ;next iter:x0=w(n-2),y0=ai2/2
;round result
;output sample
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