www.pudn.com > viterbi_wlan_c54.rar > Viterbi_upck.asm
;****************************************************************
; Filename: viterbi_upck.asm
; Function: viterbi encoder
; Version: 1.00
; Processor: C54xx
; Description: Implements the unpacking of the G0 G1 streams
; C-callable, simulate soft decsion.
;
; Useage: void viterbi_upck(int *enc,
; int *g0g1,
; ushort frame_sz)
;
;
;
; Unpack routine for encoded data
;
; This code separates the packed encoded data into individual G0 and G1 bits
; to allow simulation of transmission over a channel which induces errors.
; The received data is an array of G0 and G1 bits represented as 3-bit signed
; antipodal values (0 => 7, 1 => -7).
;
; The routine unpacks data from the 11 fully packed data words (176 bits),
; alternating between G0 and G1 data. Then it unpacks the last 13 bits
; from each data word outside the main loop.
;
; AR0 = 2 (index register for accessing output arrays)
; enc_ptr = pointer to packed encoded data (input)
; g0_ptr = pointer to unpacked encoded data (G0 array)
; g1_ptr = pointer to unpacked encoded data (G1 array)
; loop_counter = input buffer size (12 words)
;
;
;****************************************************************
.mmregs
; Far-mode adjustment
; -------------------
.if __far_mode
OFFSET .set 2
.else
OFFSET .set 1
.endif
FRAME_SZ .set 0
REG_SAVE_SZ .set 0
PARAM_OFFSET .set FRAME_SZ + REG_SAVE_SZ + OFFSET
; Register usage
; --------------
.asg 0 + REG_SAVE_SZ + FRAME_SZ, RETURN_ADDR
.asg 0 + PARAM_OFFSET, g0
.asg 1 + PARAM_OFFSET, frame_sz
.asg AR0, index
.asg AR2, enc_ptr
.asg AR3, g0_ptr
.asg AR4, g1_ptr
.asg BRC, rptb_cnt
.asg AR5, loop_counter
.asg AR1, frame_sz
;**************************************************************************
.global _viterbi_upck
_viterbi_upck
;
; Copy arguments to their local locations as necessary
;----------------------------------------------------------------
MVDK *sp(g0), g1_ptr ; 2 cycles
MVDK *sp(g0), g0_ptr ; 2 cycles
MVDK *sp(2), frame_sz ; 2 cycles
MAR *g1_ptr+ ; 1 cycle
MAR *frame_sz- ; 1 cycle
LDM frame_sz,B
SFTL B,1
ADD B, A ; A = head pointer of enc_out + (frame_sz-1)*2,
STLM A, enc_ptr ; enc_ptr point to the lastest element of enc_out
MAR *frame_sz- ; 1 cycle
LDM frame_sz, A ; 1 cycle
STLM A, loop_counter ; 1 cycle ; load j counter (11 full words/frame)
STM #2,index ; 2 cycles ; set index reg
UNPACK_LOOP ; do j=1,11 (n = 16*j-1)
STM #16-1,BRC ; 2 cycles ; load i counter (16 bits/word)
LD *enc_ptr+,A ; 1 cycle ; A = G0[n:(n-15)]
RPTB UPLOOP1_END-1 ; 4 cycles ; do i=15,0
SFTL A,-1 ; 1 cycle ; C = G0[n-i]
LD #7,B ; 1 cycle ; B = +7
NOP ; 1 cycle ; (2-word latency required)
XC 2,C ; 1 cycle ; if C==1
LD #-7,B ; 2 cycles ; B = -7 (NOTE: this creates a 16-bit #)
STL B,*g0_ptr+0 ; 1 cycle ; G0[n-i] = B
UPLOOP1_END ; end do (i loop)
STM #16-1,BRC ; 2 cycles ; load i counter (16 bits/word)
LD *enc_ptr,A ; 1 cycle ; A = G1[n:(n-15)]
RPTB UPLOOP2_END-1 ; 4 cycles ; do i=15,0
SFTL A,-1 ; 1 cycle ; C = G1[n-i]
LD #7,B ; 1 cycle ; B = +7
NOP ; 1 cycle ; (2-word latency required)
XC 2,C ; 1 cycle ; if C==1
LD #-7,B ; 2 cycles ; B = -7
STL B,*g1_ptr+0 ; 1 cycle ; G1[n-i] = B
UPLOOP2_END ; end do (i loop)
BANZD UNPACK_LOOP,*loop_counter- ;2 cycles ; end do (j loop)
MAR *+enc_ptr(-3) ; 2 cycles ; set input pointer to prior G0 word
UNPACK_LAST
STM #13-1,BRC ; 2 cycles ; load i counter (13 bits in last word)
LD *enc_ptr+,A ; 1 cycle ; A = G0[188:176]
RPTB UPLOOP3_END-1 ; 4 cycle ; do i=12,0
SFTL A,-1 ; 1 cycle ; C = G0[188-i]
LD #7,B ; 1 cycle ; B = +7
NOP ; 1 cycle ; (2-word latency required)
XC 2,C ; 1 cycle ; if C==1
LD #-7,B ; 2 cycles ; B = -7
STL B,*g0_ptr+0 ; 1 cycle ; G0[188-i] = B
UPLOOP3_END ; end do (i loop)
STM #13-1,BRC ; 2 cycles ; load i counter (13 bits in last word)
LD *enc_ptr,A ; 1 cycle ; A = G1[188:176]
RPTB UPLOOP4_END-1 ; 4 cycles ; do i=12,0
SFTL A,-1 ; 1 cycle ; C = G1[188-i]
LD #7,B ; 1 cycle ; B = +7
NOP ; 1 cycle ; (2-word latency required)
XC 2,C ; 1 cycle ; if C==1
LD #-7,B ; 2 cycles ; B = -7
STL B,*g1_ptr+0 ; 1 cycle ; G1[188-i] = B
UPLOOP4_END
;
; Restore stack to previous value, FRAME, etc..
;----------------------------------------------------------------
RETURN:
.if __far_mode
FRETD ; 4 cycles
.else
RET ; 3 cycles
.endif
;END
;end of file. please do not remove. it is left here to ensure that no lines of code are removed by any editor