Appendix
Page 38
Version FELD-V2002.02
PROFIBUS manual
The following 4 bytes were received:
(Byte 1)
(Byte 2)
(Byte 3)
(Byte 4)
(first byte received)
(last byte received)
0x3F 0x40 0x00 0x00
0011
1111b
0100
0000b
0000 0000b 0000 0000b
0
011 1111 0b
100 0000 0000 0000 0000 0000b
S=0
E=0111 1110b
M=100 0000 0000 0000 0000 0000b
S=0
E=0x7E
(dec.126) M=0x400000
The value in the mantissa field is interpreted as places after the decimal point
in the following way:
1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 b
1 * 2
-1
0 * 2
-2
0 * 2
-3
0 * 2
-4
0 * 2
-5
etc.
0 * 2
-23
The float value can now be calculated using equation <>:
75
.
0
5
.
1
*
2
1
5
.
1
*
2
1
5
.
1
*
2
*
1
)
5
.
0
0
.
1
(
*
2
*
)
1
(
1
1
)
127
126
(
0
=
=
=
=
+
−
=
−
−
x
x
x
x
The byte combination 0x3F 0x40 0x00 0x00 equals float value +0.75.