#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 09:46, local time: 2024/10/4 07:16,
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