Siemens 500 NIM - Manual (Page 126)

Floating Point Numbers B-4 SIMATIC TIWAY I Series 500 NIM User Manual
IBM Format (continued)
EXAMPLES:
Base 10 Number
Hexadecimal Contents
of Memory Word
Word 1 Word 2
1.0
0.5
-1.0
0.03125
100.0
4110
4080
C110
3F80
4264
0000
0000
0000
0000
0000
Normalized
Hexadecimal
Fraction
1st
Word
2nd
Word
Mantissa
Sign Bit
Exponent
(7 bits)
Most Significant
(8 bits)
Least Significant 16 bits of number C, D, E, F
A summary equation for IBM to decimal floating point conversion is:
Base 10 Number = (-1)
** All numbers in the above equation are hexadecimal.
MSB
bit position 0
LSB
EE A, B
* 16 * ( A * 16
s (
16
-
16
40 ) EE
S
-1
+ ...
-6
+ F * 16 )
Figure B-1 IBM Floating Point Representation