DSP56300 datasheet(83/108 Pages) FREESCALE

83 / 108 page

Extended Algorithm Program Listing

Viterbi Decoder Implementation

B-5

;*******************viterbi add, compare, select butterfly macro***

;

FUNCTION: Update path metrics/paths for the Viterbi algorithm by

;

doing an add,compare,select update for state pairs.

;

INPUTS:

;

r2 should point to the beginning of the branch metric table

;

r5 should point to the latest path metric for state 0

;

r4 should point to the storage location for updated state 0

;

n5 should offset addresses by NUMSTATES/2

;

OUTPUTS:

;

Updated path metrics/paths stored in XY memory

;

REGISTERS USED:

;

a,b,y01,r2,r4,r5,n5 r2 unchanged (modulo req'd)

;

Registers:

;

r5, pointer to the path metric/path table, arranged as

;

x: path metric, y: path,states ordered assuming

;

bits shift right to left.

;

r4, pointer to the output path metric/path table

;

r0, pointer to the branch metric table, arranged

;

as x:C, y:D, CD,CD,CD, etc.

;

SA------NSA

;

C /

;

D \

;

D /

;

SB------NSB

;

;*****************************************************************

;

ACS

macro

;

move

#BRY,r2

;r2 points to branch metrics

move

l:(r2)+,y

;get first branch metric

move

l:(r5)+n5,a

;load 1st metric/path pair

;

#NoAcs,_P_NextStage

;update each state

add

y0,a

l:(r5)-n5,b

;sum pt,br met,get next pair

add

y1,b

;update metric

max

a,b

l:(r5)+n5,a

;pick max, reload 1st pair

vsl

b,0,l:(r4)+

;save surivior, end top half

add

y1,a

l:(r5)-n5,b

;sum pt,br,reload next pair

add

y0,b

(r5)+

;sum again,inc pt mt read ptr

max

a,b

l:(r5)+n5,a

;pick max, load next pair

move

l:(r2)+,y

;load next branch metrics

vsl

b,1,l:(r4)+

;write survivor,end 2nd half

_P_NextStage

nop

;needed to separate do loop ends

endm

Example B-1

Extended Algorithm Program Listing (Continued)

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

DSP56300 Arkusz danych(PDF) 83 Page - Freescale Semiconductor, Inc

DSP56300 Arkusz danych(HTML) 83 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Arkusz danych Pobierz

Link URL