參數(shù)資料
型號(hào): DSP56600
廠商: 飛思卡爾半導(dǎo)體(中國(guó))有限公司
英文描述: Implementing Viterbi Decoders Using the VSL Instruction on DSP Families
中文描述: 維特比解碼器實(shí)現(xiàn)上使用DSP的家庭教學(xué)的VSL
文件頁(yè)數(shù): 73/108頁(yè)
文件大小: 726K
代理商: DSP56600
Basic Algorithm Program Listing
Viterbi Decoder Implementation
For More Information On This Product,
Go to: www.freescale.com
A-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,x0,y1,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
;
C
;*****************************************************************************
ACS
macro
;
;
move
#BRY,r2
move
y:(r2)+,y1
move
l:(r5)+n5,a
;
do
#NoOfAcsButt,_P_NextStage
sub
y1,a
l:(r5)-n5,b
add
y1,b
max
a,b
l:(r5)+n5,a
vsl
b,0,l:(r4)+
add
y1,a
l:(r5)-n5,b
sub
y1,b
x:(r5)+,x0
max
a,b
l:(r5)+n5,a
vsl
b,1,l:(r4)+
_P_NextStage
nop
endm
;r2 points to branch metrics
;get first branch metric
;load 1st metric/path pair
;update each state
;sub pt,br met,get next pair
;update metrics
;pick max,reload 1st pair
;store survivor,end top half
;add pt,br met,reload next pair
;inc st ptr,ld nxt br met
;pick max met,load next pair
;st survivor,end 2nd half
y:(r2)+,y1
;needed to separate do loop ends
Example A-1
Basic 16-Bit Implementation of a Viterbi Decoder (Continued)
F
Freescale Semiconductor, Inc.
n
.
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