Finisar AN-2030 User Manual
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AN-2030: Digital Diagnostic Monitoring Interface for Optical Transceivers
F i n i s a r
9/26/02 Revision D
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Table 3.16c: IEEE-754 Single-Precision Floating Point Number Format
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FUNCTION
SIGN
EXPONENT
MANTISSA
BIT
31
30……………………23
22……………………………………………………………0
BYTE
3
2
1
0
ß Most Significant Least Significant à
3
4
5
6
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Rx_PWR(4), as an example, is stored as in Table 3.16d.
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Table 3.16d: Example of Floating Point Representation
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BYTE
ADDRESS
CONTENTS
SIGNIFICANCE
56
SEEEEEEE
Most
57
EMMMMMMM
2
nd
Most
58
MMMMMMMM
2
nd
Least
59
MMMMMMMM
Least
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where S = sign bit; E = exponent bit; M = mantissa bit.
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Special cases of the various bit values are reserved to represent indeterminate values
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such as positive and negative infinity; zero; and “NaN”or not a number. NaN indicates
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an invalid result. As of this writing, explanations of the IEEE single precision floating
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point format were posted on the worldwide web at
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http://www.psc.edu/general/software/packages/ieee/ieee.html
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and
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http://research.microsoft.com/~hollasch/cgindex/coding/ieeefloat.html
.
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The actual IEEE standard is available at
www.IEEE.org
.
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