TECO 7300CV, Руководство пользователя

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7300CV MODBUS COMMUNICATION PROTOCOL
File No. :PC-CV-08
Version : 1.A
Page :
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(2) Exclusive OR the first 8-bit byte of the message with the low-order byte of the 16-bit CRC
register, putting the result in the CRC register.
(3) Shift the CRC register one bit to the right (toward the LSB), Zero-filling the MSB, Extract and
examines the LSB.
(4) (If the LSB was 0): Repeat Steps (3)(another shift).(If the LSB was 1): Exclusive OR the CRC
register with the polynomial value A001 hex (1010 0000 0000 0001).
(5) Repeat Steps (3) and (4) until 8 shifts been performed. When this is done, a complete 8-bit byte
will be processed.
(6) Repeat Steps (2) through (5) for next 8-bit byte of the message, Continue doing this until all
bytes have been processed. The final content of the CRC register is the CRC value. Placing the
CRC into the message: When the 16-bit CRC (2 8-bit bytes) is transmitted in the message, the
low-order byte will be transmitted first, followed by the high-order byte, For example, if the
CRC value is 1241 hex, the CRC-16 Upper put the 41h, the CRC-16 Lower put the 12h
z CRC calculation application program
UWORD ch_sum ( UBYTE long , UBYTE *rxdbuff ) {
BYTE i = 0;
UWORD wkg = 0xFFFF;
while ( long-- ) {
wkg ^= +;
for ( i = 0 ; i < 8; i++ ) {
if ( wkg & 0x0001 ) {
wkg = ( wkg >> 1 ) ^ 0xa001;
}
else {
wkg = wkg >> 1;
}
}
}
return( wkg );
}