Channel Decode - Motorola DSP56305 User Manual

VITERBI CO-PROCESSOR
Programming Examples
13.9.2

Channel Decode

;#############################################################################
; VCOP Decode with Rate=1/3 and Constraint_length=5
;
; Revised: June '96
;#############################################################################
START equ $100
include "ioequz.asm"
include "intequz.asm"
org P:0
jmp START
org P:START
move #$0,r0
move #$0,r4
move #$250,r5
movep #60,y:M_VCNT
movep #$1c45,y:M_VTPA ; tapa=1+D+D^3+D^4,tapb=1+D^2+D^4,tapc=1+D+D^2+D^3+D^4
movep #$0000,y:M_VTSR ; ES=0,IS=0
movep #$1010,y:M_VWES ; set WED start location and window length
movep #$0041,y:M_VCRB ; Init_state,Max_path enable,WED enable
;
movep #$1105,y:M_VCRA ; Enable Decoding at Rate 1/3 cnst=5
do #61,endd
jclr #8,y:M_VSTR,*
;
rep #3
movep x:(r0)+,y:M_VDR ; read input symbols
nop
nop
endd
jclr #5,y:M_VSTR,*
jclr #6,y:M_VSTR,*
;
movep y:M_VBER,y:(r4)+ ; read BER (Rx Qual) value
movep y:M_VWED,y:(r4)+ ; read WED value
;
rep #61
movep y:M_VDOR,y:(r5)+
jclr #4,y:M_VSTR,*
stop
org x:$0
dc
dc
dc
13-40
; pointer to input symbols.
; pointer to BER and WED results
; Output Buffer
; 61 decoded bits
; wait till DREQ
; pipeline delay
; (see section B-5.1 in DSP56300 Family Manual)
; wait till Proc_Done
; wait till DRDY
; read decoded bits from output buffer
; wait till OPC
; Input to decoder, 61x3 symbols
$800000
$800000
$800000
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