GE Multilin
B90 Low Impedance Bus Differential System
B-3
APPENDIX B
B.1 MODBUS RTU PROTOCOL
B
Table B–3: MODBUS RTU CRC-16 ALGORITHM
SYMBOLS:
-->
data transfer
A
16 bit working register
Alow
low order byte of A
Ahigh
high order byte of A
CRC
16 bit CRC-16 result
i,j
loop counters
(+)
logical EXCLUSIVE-OR operator
N
total number of data bytes
Di
i-th data byte (i = 0 to N-1)
G
16 bit characteristic polynomial = 1010000000000001 (binary) with MSbit dropped and bit order reversed
shr (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 bits
are shifted right one location)
ALGORITHM:
1.
FFFF (hex) --> A
2.
0 --> i
3.
0 --> j
4.
Di (+) Alow --> Alow
5.
j + 1 --> j
6.
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: continue
9.
i + 1 --> i
10.
Is i = N?
No: go to 3; Yes: continue
11.
A --> CRC
Summary of Contents for B90
Page 10: ...x B90 Low Impedance Bus Differential System GE Multilin TABLE OF CONTENTS ...
Page 284: ...5 166 B90 Low Impedance Bus Differential System GE Multilin 5 8 TESTING 5 SETTINGS 5 ...
Page 334: ...10 8 B90 Low Impedance Bus Differential System GE Multilin 10 2 BATTERIES 10 MAINTENANCE 10 ...
Page 338: ...A 4 B90 Low Impedance Bus Differential System GE Multilin A 1 PARAMETER LISTS APPENDIX A A ...
Page 460: ...C 30 B90 Low Impedance Bus Differential System GE Multilin C 7 LOGICAL NODES APPENDIX C C ...
Page 476: ...E 10 B90 Low Impedance Bus Differential System GE Multilin E 1 IEC 60870 5 104 APPENDIX E E ...
Page 502: ...viii B90 Low Impedance Bus Differential System GE Multilin INDEX ...