4-3
ENGLISH
Read registers
MODBUS protocol manual
4.1 Floating point as per IEEE Standard
(not available for MODBUS TCP)
The basic format allows a IEEE standard floating-point number to be represented in a single-32 bit
format, as shown below:
N.n = (-1)
S
2
e’-127
(1.f )
where S is the sign bit, e’ is the first part of the exponent and f is the decimal fraction placed next
to 1. Internally the exponent is 8 bits in length and the stored fraction is 23 bits long.
The floating-point format is shown as follows:
======================
| S | e + 127 | f |
======================
31 30 23 22 0 <—
bit number
where:
bit length
Sign 1
Exponent 8
Fraction 23 + (1)
Total m = 32 + (1)
Exponent
Min e’ 0
Max e’ 255
Bias 127
NOTE
Fractions (decimals) are always shown while the leading 1 (hidden bit) is not stored.
See section 7 for the Registers Table.
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