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FC410 with Modbus
Operating Instructions, 02/2016, A5E33120874-AC
151
Float definition
F
F.1
Float definition
Stuffing of multi-byte numbers into multiple Modbus RTU registers differs among Modbus
devices. "Big Endian" and "Little Endian" describe the order or sequence in which multi-byte
data is stored in memory. This device uses (IEEE 741) a "Big-Endian" representation for
addresses and data items as default. This means that when a numerical quantity larger than
a single byte is transmitted, the MOST significant byte is sent first.
Float transmission order can be changed as described in Float transmission (Page 77).
Following example describes the Big-Endian representing of float IEEE741.
Value (decimal)
IEEE FP B MSB
LSB
Register N
Register N + 1
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
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