GE B30 UR Series Instruction Manual

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Contents

GE Multilin B30 Bus Differential System B-3APPENDIX B B.1 MODBUS RTU PROTOCOLBTable B–3: CRC-16 ALGORITHMSYMBOLS: --> data transferA 16 bit working registerAlow low order byte of AAhigh high order byte of ACRC 16 bit CRC-16 resulti,j loop counters(+) logical EXCLUSIVE-OR operatorN total number of data bytesDi i-th data byte (i = 0 to N-1)G 16 bit characteristic polynomial = 1010000000000001 (binary) with MSbit dropped and bit order reversedshr (x) right shift operator (th LSbit of x is shifted into a carry flag, a '0' is shifted into the MSbit of x, all other bitsare shifted right one location)ALGORITHM: 1. FFFF (hex) --> A2. 0 --> i3. 0 --> j4. Di (+) Alow --> Alow5. j + 1 --> j6. shr (A)7. Is there a carry? No: go to 8; Yes: G (+) A --> A and continue.8. Is j = 8? No: go to 5; Yes: continue9. i + 1 --> i10. Is i = N? No: go to 3; Yes: continue11. A --> CRC