Manual

ALTOSONIC V
ModBus Manual 0300 rev07 E 7.30855.35.00 Page 17 of 64
6.1 Floating Point Representation
The exponent is biased by 127.
The mantissa is 24 bits with the most significant bit 1 (not stored), 23 bit stored.
Biased exponent Mantissa 3 (high) Mantissa 2 Mantissa 1 (low)
SEEE EEEE E MMM MMMM MMMM MMMM MMMM MMMM
6.2 Double Representation
The exponent is biased by 1023.
The mantissa is 53 bits with the most significant bit 1 (not stored), 52 bits stored.
Biased exponent Exp+Mantissa Mantissa 6 Mantissa 5
SEEE EEEE EEEE MMMM MMMM MMMM MMMM MMMM
Mantissa 4 Mantissa 3 Mantissa 2 Mantissa 1
MMMM MMMM MMMM MMMM MMMM MMMM MMMM MMMM
6.3 Transmit Sequence
Integers are transmitted and stored with the most significant part first.
Example
Integer value 1790 decimal (6FE hexadecimal) is transmitted as:
First transmitted byte in data field Second transmitted byte in data field
06 FE
Long integers could be transmitted in two possible ways:
Example
Long integer value 305419896 (12345678 hexadecimal)
The transmit order in both modes:
Normal mode (1)
12
h
(2)
34
h
(3)
56
h
(4)
78
h
Reversed mode (3)
56
h
(4)
78
h
(1)
12
h
(2)
34
h
Floats could be transmitted in two ways:
Example:
The float number 4.125977 will give the IEEE representation.
S EXPONENT MANTISSA
0 1000 0001 (1) 000 0100 0000 1000 0000 0000
• A biased exponent of 129 (81 hexadecimal) is exponent 2.
• A positive sign
• Mantissa = 4 + 1/8 + 1/1024. Note that the first bit is not stored!