Data Video SE-2850, Руководство пользователя

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MANDATORY ANNEX 3
CRC CALCULATION
CRCL and CRCH are the bytes for the 16-bit control word (herein the Annex 3 it may
be called check sum). All the bytes except the last 2 bytes from a block are used to
calculate the check sum. There must be 0x0000 after the check sum calculation
including the last 2 bytes if the data have been transmitted error free.
The initial value for check sum calculation is 0xFFFF. CRCL and CRCH can be
calculated, particularly, by means of the tables A3.1 and A3.2 according to the rule
below:
CRCH’ = Tbl.A3.2 (I),
CRCL’ = Tbl.A3.1 (I) + CRCH, where I = CRCL + InputByte
CRCH and CRCL correspond to higher and lower byte of the current check sum value,
InputByte is the next data byte. CRCH’ and CRCL’ correspond to higher and lower
byte of the new check sum value. Tbl.A3.2 (I) and Tbl.A3.1 (I) correspond to the
tables' values, I is the shift factor in the tables. «+» means bit-wise XOR.
Table A3.1. Lower CRC byte calculation coefficients.
000h 0c1h 081h 040h 001h 0c0h 080h 041h
001h 0c0h 080h 041h 000h 0c1h 081h 040h
001h 0c0h 080h 041h 000h 0c1h 081h 040h
000h 0c1h 081h 040h 001h 0c0h 080h 041h
001h 0c0h 080h 041h 000h 0c1h 081h 040h
000h 0c1h 081h 040h 001h 0c0h 080h 041h
000h 0c1h 081h 040h 001h 0c0h 080h 041h
001h 0c0h 080h 041h 000h 0c1h 081h 040h
001h 0c0h 080h 041h 000h 0c1h 081h 040h
000h 0c1h 081h 040h 001h 0c0h 080h 041h
000h 0c1h 081h 040h 001h 0c0h 080h 041h
001h 0c0h 080h 041h 000h 0c1h 081h 040h
000h 0c1h 081h 040h 001h 0c0h 080h 041h
001h 0c0h 080h 041h 000h 0c1h 081h 040h
001h 0c0h 080h 041h 000h 0c1h 081h 040h