; ; From Dallas Application note 27 ; ; CRC-16 (x^16+x^15+x^2+x^0) ; No tables, No loops, No temporary registers used. ; ; This code is from Dallas Semiconductor Application Note 27: ; ; Understanding and Using Cyclic Redundancy Checks ; with Dallas Semiconductor iButton(TM) Products. ; ; This routine that calculates the same CRC as the hardware ; in the DS5001/2 secure micro. ;----------------------------------------------------------------------- NAME CRC_test ?DT?CRC_test SEGMENT DATA rseg ?DT?CRC_test CRCH: ds 1 CRCL: ds 1 ?CO?CRC_test SEGMENT CODE RSEG ?CO?CRC_test public CRC_test CRC_test: mov CRCH,#0 mov CRCL,#0 mov A,#080H call CRC16 mov A,#075H call CRC16 mov A,#08AH call CRC16 mov A,#00BH call CRC16 mov A,#075H call CRC16 mov A,#0C7H call CRC16 mov A,#0AAH call CRC16 mov A,#075H call CRC16 mov A,#0C7H call CRC16 mov A,#055H call CRC16 mov A,#043H call CRC16 ljmp CRC_test ;CALCULATE CRC16 IN PARALLEL TO THE GREATEST EXTENT PRACTICAL ; INPUT: BYTE TO BE INCUDED IN CRC CALCULATION IS IN ACC ; OUTPUT: CRCH:CRCL UPDATED TO INCLUDE THE NEW BYTE ; CRC16: PUSH ACC ;save this in case the caller needs it XRL A,CRCL MOV CRCL,CRCH ;put the high byte of the crc in its dest.. MOV CRCH,A ;save data xor low(crc) for later MOV C,P JNC CRC0 XRL CRCL,#001H CRC0: RRC A ;get the low bit in c JNC CRC1 XRL CRCL,#040H CRC1: MOV C,ACC.7 XRL A,CRCH ;compute the results for bits P...U RRC A ;shift them into place MOV CRCH,A ;and save them JNC CRC2 XRL CRCL,#080H CRC2: POP ACC ;and restore everything and return RET end
file: /Techref/8051/crc16.htm, 2KB, , updated: 2001/4/17 10:21, local time: 2024/8/21 13:12,
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