SH7261 Datasheet, PDF (100/1348 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7260 Series

Section 3 Floating-Point Unit (FPU)
63 62
52 51
0
s
e
f
Figure 3.2 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 3.1 shows E_min and E_max values.
Table 3.1 Floating-Point Number Formats and Parameters
Parameter
Total bit width
Sign bit
Exponent field
Fraction field
Precision
Bias
E
max
E
min
Single-Precision
32 bits
1 bit
8 bits
23 bits
24 bits
+127
+127
–126
Double-Precision
64 bits
1 bit
11 bits
52 bits
53 bits
+1023
+1023
–1022
Floating-point number value v is determined as follows:
If E = E_max + 1 and f ≠ 0, v is a non-number (NaN) irrespective of sign s
If E = E_max + 1 and f = 0, v = (–1)^s (infinity) [positive or negative infinity]
If E_min ≤ E ≤ E_max, v = (–1)^s2^E (1.f) [normalized number]
If E = E_min – 1 and f ≠ 0, v = (–1)^s2^Emin (0.f) [denormalized number]
If E = E_min – 1 and f = 0, v = (–1)^s0 [positive or negative zero]
Table 3.2 shows the ranges of the various numbers in hexadecimal notation.
Rev. 2.00 Sep. 07, 2007 Page 68 of 1312
REJ09B0320-0200