Serial Interface Manual
•
TLS2 Monitoring Systems
Part No. 577013-767, Revision H
5
6.3
ASCII FLOATING POINT FORMAT
6.3.1
NOTES
6.3.1.1
HHHHHHHH (H = 0-9 or A-F) indicates the 8 "nibble" ASCII-Hexadecimal representation of
a 4-Byte Floating Point number. Many data parameters are transmitted in this format.
6.3.1.2
The 32-bits are arranged as follows:
Byte
1
2
3
4
S EEE
EEEE
E MMM
MMMM
MMMM
MMMM
MMMM
MMMM
Nibble
1
2
3
4
5
6
7
8
S is the sign bit (0 if positive, 1 if negative).
EEE EEEE E represents the 2's exponent. It is a 2's complement value biased by 127 (7F
Hex). The exponent can be determined by subtracting 127 from the value of the E field and
raising 2 to the resulting power.
MMM MMMM MMMM MMMM MMMM MMMM represents the 23-bit mantissa. Since
the mantissa describes a value which is greater than or equal to 1.0 and less than 2.0, the 24th
bit is always assumed to be equal to 1 and is not transmitted or stored. The value of the
mantissa can be determined by dividing the value of the M field by 8,388,608 (2
23
) and adding
1.0.
6.3.1.3
The complete value of the floating point number can then be determined by multiplying the
exponent by the mantissa and attaching the appropriate positive or negative sign.
6.3.1.4
By convention, 00 00 00 00 represents the value 0.0 even though it actually converts to 5.8775
x 10
-39
.
6.3.1.5
The eight "nibbles" are transmitted in sequence from 1 through 8 as shown in section 6.3.1.2.
