www.pudn.com > viterbi_wlan_c54.rar > wlan_enc.asm
;****************************************************************
; Filename: wlan_enc.asm
; Function: Convolutional encoder
; Version: 1.00
; Processor: C54xx
; Author: LiuKai vikingpro@163.com
; Description: Implements the 802.11 convolutional encoder
; C-callable
;
; Useage: ushort wlan_enc(int *frame,
; int *output,
; ushort frame_sz,
; )
;
; Convolutional encoder for 802.11: R=1/2, K=7
;
; G0 = x(n) + x(n-2) + x(n-3) + x(n-5) + x(n-6)
; G1 = x(n) + x(n-1) + x(n-2) + x(n-3) + x(n-6)
;
; This code operates on packed input data and outputs packed output data
; in the form G0(15-0), G1(15-0), G0(31-16), G1(31-16), etc. The first
; word, G0/G1[17-16], sets the top 6 unused bits to zero.
;
;****************************************************************
.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, output
.asg 1 + PARAM_OFFSET, frame_sz
.asg AR3, output_ptr
.asg AR4, frame_ptr
.asg BRC, rptb_cnt
;**************************************************************************
.global _wlan_enc
_wlan_enc
;
; Copy arguments to their local locations as necessary
;----------------------------------------------------------------
STLM A, frame_ptr ; 1 cycle
MVDK *sp(output), output_ptr ; 2 cycles
;
; Set outer loop count by subtracting 1 from nsamps and
; storing into block repeat count register
;----------------------------------------------------------------
LD *sp(frame_sz), A ; 1 cycle
SUB #1, A ; 2 cycles
STLM A, rptb_cnt ; 1 cycle
NOP ; 1 cycle
;
; Begin outer loop on # samples
;----------------------------------------------------------------
;_start:
RPTB ENCODE_END-1 ; 4 cycles ; do i= rptb_cnt,0
LD *frame_ptr+,16,A ; 1 cycle ; AHI = X[n :(n-15)]
OR *frame_ptr-,A ; 1 cycle ; ALO = X[n-16):(n-31)]
LD *frame_ptr+,16,B ; 1 cycle ; BHI = X[n :(n-15)]
OR *frame_ptr,B ; 1 cycle ; BLO = X[n-16 :(n-31)]
XOR B,2,A ; 1 cycle ; A = X(n) XOR X(n-2)
XOR B,3,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3)
XOR B,6,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6)
XOR B,5,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6) XOR X(n-5)
STH A,*output_ptr+ ; 1 cycle ; save G0[n:(n-15)]
XOR B,5,A ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6)
XOR B,1,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6) XOR X(n-1)
STH A,*output_ptr+ ; 1 cycle ; save G1[n:(n-15)]
ENCODE_END:
; Last loop has low word = 0000h
LD *frame_ptr,16,A ; 1 cycle ; AHI = X[15:0]
LD *frame_ptr,16,B ; 1 cycle ; BHI = X[15:0]
XOR B,2,A ; 1 cycle ; A = X(n) XOR X(n-2)
XOR B,3,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3)
XOR B,6,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6)
XOR B,5,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6) XOR X(n-5)
STH A,*output_ptr+ ; 1 cycle ; save G0[n:(n-15)]
XOR B,5,A ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6)
XOR B,1,A ; 1 cycle ; A = X(n) XOR X(n-2) XOR X(n-3) XOR X(n-6) XOR X(n-1)
STH A,*output_ptr- ; 1 cycle ; save G1[n:(n-15)]
_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