Altera Floating-Point Manual do Utilizador Página 20

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Figure 1-9: Single-Precision Representation
This figure shows a single-precision representation.
S E M
31 30 23 22 0
Double-Precision Format
The double-precision format contains the following binary patterns:
The MSB holds the sign bit.
The next 11 bits hold the exponent bits.
52 LSBs hold the mantissa.
The total width of a floating-point number in the double-precision format is 64 bits. The bias for the
double-precision format is 1023.
Figure 1-10: Double-Precision Representation
This figure shows a double-precision representation.
S E M
63 62 52 51 0
Single-Extended Precision Format
The single-extended precision format contains the following binary patterns:
The MSB holds the sign bit.
The exponent and mantissa fields do not have fixed widths.
The minimum exponent field width is 11 bits and must be less than the width of the mantissa field.
The width of the mantissa field must be a minimum of 31 bits.
The sum of the widths of the sign bit, exponent field, and mantissa field must be a minimum of 43 bits
and a maximum of 64 bits. The bias for the single-extended precision format is unspecified in the
IEEE-754 standard. In these IP cores, a bias of 2
(
WIDTH_EXP–1
)
1 is assumed for the single-extended
precision format.
Special Case Numbers
The following table lists the special case numbers defined by the IEEE-754 standard and the data bit
representations.
Table 1-4: Special Case Numbers in IEEE-754 Representation
Meaning Sign Field Exponent Field Mantissa Field
Zero Don’t care All 0’s All 0’s
Positive Denormalized 0 All 0’s Non-zero
1-14
Double-Precision Format
UG-01058
2014.12.19
Altera Corporation
About Floating-Point IP Cores
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