#include <stdio.h>
/********************************************************************
CRC-16 (x^16+x^15+x^2+x^0)
No tables, No jumps.
Input: c = Data byte for CRC calculation
usp_crc = pointer to 16 bit CRC register
Output: CRC at pointer usp_crc is updated
Copyright (C) February 11, 2000. All Right Reserved.
Charles Ader, PO Box 940 Pleasanton, California, USA.
This code started out as an example program found in
Dallas Semiconductor Application Note 27:
Understanding and Using Cyclic Redundancy Checks
with Dallas Semiconductor iButton(TM) Products.
The application note shows an 8051 assembly language
routine that calculates the same CRC as the hardware
in the DS5001/2 secure micro.
********************************************************************/
void crc16(unsigned short *usp_crc, unsigned char c)
{
unsigned short crc; /* use a local temp so the compiler will */
/* handle all the x86 pointer crap. */
crc = *usp_crc;
_asm {
mov al,c
mov cx,crc
XOR AL,CL
MOV CL,CH
MOV CH,AL
LAHF
NOT AH
RCR AH,1
RCR AH,1
AND AH,1
XOR CL,AH
RCR AX,1
SBB AH,AH
AND AH,0x40
XOR CL,AH
MOV AH,AL
XOR AL,CH
RCL AH,1
RCR AL,1
MOV CH,AL
RCR AL,1
AND AL,0x80
XOR CL,AL
mov crc,cx
}
*usp_crc = crc;
}
/******************************************************
* MAIN FUNCTION *
*******************************************************/
main()
{
unsigned int crc;
while(1) {
crc = 0; /* crc = 0x0000 */
crc16(&crc,0x80); /* crc = 0xA001 */
crc16(&crc,0x75); /* crc = 0x27A0 */
crc16(&crc,0x8A); /* crc = 0xDFA6 */
crc16(&crc,0x0B); /* crc = 0xBD1E */
crc16(&crc,0x75); /* crc = 0xEFFC */
crc16(&crc,0xC7); /* crc = 0xD3AE */
crc16(&crc,0xAA); /* crc = 0xC3D2 */
crc16(&crc,0x75); /* crc = 0xBA82 */
crc16(&crc,0xC7); /* crc = 0xF37B */
crc16(&crc,0x55); /* crc = 0x1C73 */
crc16(&crc,0x43); /* crc = 0x141C */
crc16(&crc,0x1C); /* crc = 0x0014 */
crc16(&crc,0x14); /* crc = 0x0000 */
}
} /* end of main */
file: /Techref/intel/16bit/crc16.htm, 2KB, , updated: 2000/2/23 08:46, local time: 2024/12/24 21:15,
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