Mantissa And Sign; Exponent - Honeywell UMC800 Reference Manual

4.6.2 Mantissa and Sign

The mantissa is defined by a sign bit (31) and a 23-bit binary fraction. This binary fraction is combined with
an "implied" value of 1 to create a mantissa value which is greater than or equal to 1.0 and less than 2.0.
The mantissa is positive if the sign bit is zero (reset), and negative if the sign bit is one (set). For example:
DECIMAL
100
The sign bit is zero, indicating a positive mantissa. Removing the sign bits and exponent bits, the mantissa
becomes:
HEXADECIMAL
480000
Add an "implied" value of one to the left of the binary point:
Using positioned notation, this binary number is equal to:
+
-1
1 0 . ( 1 x2 ) (

4.6.3 Exponent

The exponent is defined by an unsigned 8-bit binary value (bits 23 through 30). The value of the exponent
is derived by performing a signed subtraction of 127 (decimal) from the 8-bit exponent value.
DECIMAL
100
removing the sign and mantissa bits, the exponent becomes:
DECIMAL
133
or:
1x2
Subtract a bias of 127 from the exponent to determine its value: 133 – 127 = 6.
8/99
HEXADECIMAL
42C80000
xxxxxxxx x1001000 00000000 00000000
1.1001000 00000000 00000000
+ + +
-2 -3
0 x2 ) ( 0 x2 ) (
HEXADECIMAL
42C80000
HEXADECIMAL
85
+ + +
7 6 5
0 2 x 0 x2
RS232 Communications Reference Manual
BINARY
01000010 11001000 00000000 00000000
BINARY
BINARY
= + +
-4
1 x2 ) 10 0 5 0 0 0 0 0 0625 15625 . . .
BINARY
01000010 11001000 00000000 00000000
BINARY
x1000010 1xxxxxxx xxxxxxxx xxxxxxxx
+ + +
4 3 2
0 x2 0 x2 1 x2
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+ + =
. . .
+
1 0
0 x2 1 x2
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