vgetsc.v

这是韩国EQUATOR公司提供的DEMO程序

/**
*** Copyright (c) 2001 Equator Technologies, Inc.
**/

//----------------------------------------------------------------

I_GET_STARTCODE_SUBR:

   #ifdef DUMP_SYMBOL
    setacc D0_DATA;
    setreg dbgPtr_r27;
   #endif

      // STATUS
      setacc 0xac;               
      setreg tmpData_r16;    
      setacc D0_STATUS+2;     
      nop;
      st     tmpData_r16,acc; 
      nop;

//
// Start of while() loop in startcodeloop() psg
//
I_WHILE1_STARTCODE:

    call.gbstall pcaddr_r19;  // Stall until GB has data 
    gb G_ALIGN, 3;
    nop;

I_GET_STARTCODE_SUBR_1:

    br I_TEST_FLUSH_JUNK; 
    nop;

  I_WHILE_FLUSH_JUNK:
    call.gbstall pcaddr_r19;  // Stall until GB has data 
    gb G_GETSYM, 1; // Shift 1 bit at a time...start code can be anywhere.
      nop;
      nop;
      nop;
      nop;

  I_TEST_FLUSH_JUNK:  

     #ifdef DUMP_SYMBOL
      // DUMP SYMBOL 1
      st    symbol, dbgPtr_r27; 
      add.w dbgPtr_r27, 4;
      nop;
      st    tmpData_r16, dbgPtr_r27; 
      add.w dbgPtr_r27, 4;
     #endif

    add symbol, 0;
    br.accne0 I_WHILE_FLUSH_JUNK;  // br if symbol not 16 0s, else fall-through
    nop;

I_GET_STARTCODE_SUBR_2:  

      // STATUS
      setacc 0x1ac;               
      setreg tmpData_r16;    
      setacc D0_STATUS+3;     
      nop;
      st     tmpData_r16,acc; 
      nop;

    call.gbstall pcaddr_r19;  // Stall until GB has data 
    gb G_GETSYM, 16; // Found 16 consecutive 0s, flush them out
      nop;
      nop;
      nop;
      nop;

     #ifdef DUMP_SYMBOL
      // DUMP SYMBOL 2
      st    symbol, dbgPtr_r27; 
      add.w dbgPtr_r27, 4;
      nop;
      st    tmpData_r16, dbgPtr_r27; 
      add.w dbgPtr_r27, 4;
     #endif

    br I_TEST_STARTCODE_CHECK;
    nop;

//
// 16 consecutive 0s found...check if startcode...
//   ~ If not, shift by 1 until we get either start code or other nonzero
//   ~ If other nonzero, start from beginning.
//
I_WHILE_STARTCODE_CHECK:

    call.gbstall pcaddr_r19;  // Stall routine untill GB has data 
    gb G_GETSYM, 1; // Shift 1 bit at a time...start code can be anywhere.
      nop;
      nop;
      nop;
      nop;

     #ifdef DUMP_SYMBOL
      // DUMP SYMBOL 3
      st    symbol, dbgPtr_r27; 
      add.w dbgPtr_r27, 4;
      nop;
      st    tmpData_r16, dbgPtr_r27; 
      add.w dbgPtr_r27, 4;
     #endif

I_TEST_STARTCODE_CHECK:

      // STATUS
      setacc 0x2ac;               
      setreg tmpData_r16;    
      setacc D0_STATUS+2;     
      nop;
      st     tmpData_r16,acc; 
      nop;

    // Currently only checking for the 7 0s followed by a 1, not for the 0x1c (sc value)
    swapsr symbol, _SWAP+8; // swap , then shift right by 8, acc = symbol[0:7]
    sub acc, 1;
    br.acceq0 I_GOOD_START_CODE_VALUE;  // br if symbol[0:7]==0000_0001, else...
    nop;
    swapsr symbol, _SWAP+8; // swap , then shift right by 8, acc = symbol[0:7]
    //br.accne0 I_TEST_FLUSH_JUNK;  // br if symbol[0:7] != 0000_0001 and != 0000_0000 (i.e., more junk)
    br.accne0 I_WRAP_UP;
    nop;
    br I_WHILE_STARTCODE_CHECK; // ...else symbol[0:7] == 0000_0000, so keep shifting out 0s per bit
    nop;

I_GOOD_START_CODE_VALUE:

    // Indicate found
    setacc 0xcc;              
    setreg tmpData_r16;   
    setacc D0_STATUS+2;     
    st     tmpData_r16,acc; 
    nop;

    call.gbstall pcaddr_r19;  // Stall routine untill GB has data 
    gb G_GETSYM, 16; // Shift out start code, align to coeff vlcs
      nop;
      nop;
      nop;
      nop;