Микроконтроллеры

unsigned short CRC (char *msg, int len)

{

  // 0xFFFF initial & poly 0x1021 - CCITT CRC16

  unsigned short crc=0xFFFF;

  unsigned short poly=0x1021;



  _asm {



    mov   esi,[msg]



l_char:

    lodsb

    mov   dl,al

    mov   ax,[crc]

    mov   ecx,8

l_crc:

    rcl   dl,1

    rcl   ax,1

    jnc   no_xor

    xor   ax,[poly]

no_xor:

    loop  l_crc

    mov   [crc],ax

    mov   eax,[len]

    dec   eax

    mov   [len],eax

    jnz   l_char

    mov   ecx,16

    mov   ax,[crc]

l_augment:

    shl   ax,1

    jnc   no_xor1

    xor   ax,[poly]

no_xor1:

    loop  l_augment

    mov   [crc],ax

  }



  return crc;

}









int main(int argc, char* argv[])

{



  unsigned short crc;

  char *msg="123456789";



  crc=CRC(msg,9);



	printf("%04x\n",crc); // valid = 0xe5cc

	return 0;

}