Renesas SH7781 用户手册
6. Floating-Point Unit (FPU)
Rev.1.00 Jan. 10, 2008 Page 126 of 1658
REJ09B0261-0100
REJ09B0261-0100
6.2
Data Formats
6.2.1
Floating-Point Format
A floating-point number consists of the following three fields:
• Sign bit (s)
• Exponent field (e)
• Fraction field (f)
• Exponent field (e)
• Fraction field (f)
This LSI can handle single-precision and double-precision floating-point numbers, using the
formats shown in figures 6.1 and 6.2.
formats shown in figures 6.1 and 6.2.
31
s
e
f
30
23 22
0
Figure 6.1 Format of Single-Precision Floating-Point Number
63
s
e
f
62
52
51
0
Figure 6.2 Format of Double-Precision Floating-Point Number
The exponent is expressed in biased form, as follows:
e = E + bias
The range of unbiased exponent E is E
min
– 1 to E
max
+ 1. The two values E
min
– 1 and E
max
+ 1 are
distinguished as follows. E
min
– 1 indicates zero (both positive and negative sign) and a
denormalized number, and E
max
+ 1 indicates positive or negative infinity or a non-number (NaN).
Table 6.1 shows floating-point formats and parameters.