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Modbus connection (option) System 2020 XT C
ONNECT
7 - 10
ba75970e01 10/2012
* MSB = Most significant bit, LSB = Least significant bit
If not all of the bits of the exponent are 0, the value is calculated accord
-
ing to:
If all of the bits of the exponent are 0, the value is calculated according
to:
A value is 0 if all the bits of both the exponent as well as the mantissa
are 0.
Apart from the byte order described in the bit representation, another
order of the bytes is also possible.
Opposite to the order described, the two lower bytes have been ex
-
changed with the two upper bytes in this order (b4 b3 b2 b1
-
b2 b1 b4
b3).
For Modbus applications that can independently interpret floating point
numbers (or allow to select a data format for certain registers), the byte
order the data interpretation is based on should be checked.
INT16 In the INT16 format, the data for the sensor model and status info is
transmitted. The data consists of two bytes. The assignment is carried
out in Motorola format ("big-endian", the higher value byte first).
Bit representation Byte Bit
4 31 - 24 S = sign (bit 31)
E = Exponent (Bit 30-23)
M = mantissa (bits 22-0)
3 23 - 16
2 15 - 08
1 07 - 00
If the measured value is equal to 0, check the measured
value status. If the measured value status is not equal to 1,
an error has occurred and the measured value is invalid.
The Modbus protocol does not define how the bytes of 32-
Bit-IEEE-754 floating point numbers should be ordered.
MSB* LSB*
S E E E E E E E
E M M M M M M M
M M M M M M M M
M M M M M M M M
) 2 ... 2 2 2 1 ( 2 1
23
0
3
20
2
21
1
22
127
− − − − −
⋅ + + ⋅ + ⋅ + ⋅ + ⋅ ⋅ − =
b b b b
E S
M M M M V
) 2 ... 2 2 2 ( 2 1
23
0
3
20
2
21
1
22
126
− − − − −
⋅ + + ⋅ + ⋅ + ⋅ ⋅ ⋅ − =
b b b b
S
M M M M V