bpsk.asm

adsp blackfin系列的通信QAM编码标准程序

/*******************************************************************************
Copyright(c) 2000 - 2002 Analog Devices. All Rights Reserved.
Developed by Joint Development Software Application Team, IPDC, Bangalore, India
for Blackfin DSPs  ( Micro Signal Architecture 1.0 specification).

By using this module you agree to the terms of the Analog Devices License
Agreement for DSP Software. 
********************************************************************************
Module Name     : bpsk.asm
Label name      : __bpsk
Version         : 1.3
Change History  :

                Version     Date          Author        Comments
                1.3         11/18/2002    Swarnalatha   Tested with VDSP++ 3.0
                                                        compiler 6.2.2 on 
                                                        ADSP-21535 Rev.0.2
                1.2         11/13/2002    Swarnalatha   Tested with VDSP++ 3.0
                                                        on ADSP-21535 Rev. 0.2
                1.1         03/05/2002    Sunder        Modified to match
                                                        silicon cycle count
                1.0         10/19/2001    Sunder        Original 

Description     : This routine maps input bits to output symbols according to 
                  the following rule:
                 BITS   Symbols
                  0        -1
                  1         1

Assumptions     : 1. The bitstream is stored in a character array where the 
                     start of the bitstream is at the LSB of the first character

                  2. All the characters are full (i.e. the bitstream size is at 
                  least a multiple of 8)

                  3. Since two characters from the input bitstream are read at a
                     time, the bitstream size should be a multiple of 16

Prototype       :   void __bpsk(int n, char in[], char out[]);

Registers Used  : R0-R3, I0, L0, P0-P2, LC0, LC1.

Performance     :
                    Code size   : 48 Bytes
                    Cycle count : 144 Cycles (For no of characters, n = 4)
*******************************************************************************/
.section L1_code;
.global    __bpsk;
.align 8;
    
__bpsk:
    
    L0 = 0;
    I0 = R1;                //Address of input bitstream in I0    
    P1 = R0;                //counter
    P0 = R2;                //address of output bitstream in P0
    P2 = 16(Z);             //inner loop counter
    R3 = -1;                //Symbol for bit '0' in bitstream
    R0.L = W[I0++];
    
    LSETUP(OUT_LOOP_START,OUT_LOOP_END) LC0 = P1 >> 1;
                            //Load N/2 where N is no. of chars in LC0 
OUT_LOOP_START:

        LSETUP(IN_LOOP_START,IN_LOOP_END) LC1 = P2;
IN_LOOP_START:
            CC = BITTST(R0,0);
                            //Test the last bit 
            R2 = 1(Z);
            IF !CC R2 = R3; //If bit is zero output -1 else 1
IN_LOOP_END:
            R0 = R0 >> 1 || B[P0++] = R2;
    
OUT_LOOP_END:
        R0.L = W[I0++];
    
    RTS;
    NOP;                    //to avoid one stall if LINK or UNLINK happens to be
                            //the next instruction after RTS in the memory.
__bpsk.end: