Modbus RTU RS-485
35
SFIDK.PS.023.D2.02
APPENDIX H
APPENDIX H
Float Definition
Stuffing of multi-byte numbers into multiple Modbus RTU registers differs among Modbus
devises.
„Big Endian“ and „Little Endian“ describe the order or sequence in which multi-byte data is stored
in memory. This device uses (as IEEE and Honeywell) a ‘Big-Endian’ representation for
addresses and data items. This means that when a numerical quantity larger than a single byte
is transmitted, the MOST significant byte is sent first.
Read absolute massflow (4:03001)
Query: 01,03,0B,B8,00,02,46,0A
Response: 01,03,04,40,C3,52,93,62,C8
Absolute massflow = 6.10383 kg/s
Value IEEE FP B Register N Register N + 1
(decimal) MSB LSB high low high low
100.0 42C80000h 42h C8h 00h 00h
55.32 425D47AEh 42h 5Dh 47h AEh
2.0 40000000h 40h 00h 00h 00h
1.0 3F800000h 3Fh 80h 00h 00h
-1.0 BF800000h bFh 80h 00h 00h
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