SH7058 Datasheet, PDF (106/1130 Pages) Renesas Technology Corp – Renesas SuperHTM RISC engine

3.3 Floating-Point Format
3.3.1 Floating-Point Format
The SH7058 supports single-precision floating-point operations, and fully complies with the
IEEE754 floating-point standard.
A floating-point number consists of the following three fields:
• Sign (s)
• Exponent (e)
• Fraction (f)
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).
In a single-precision operation, the bias value is 127, E_min is –126, and E_max is 127.
31 30
23 22
0
s
e
f
Figure 3.3 Floating-Point Number Format
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]
Rev. 3.0, 09/04, page 65 of 1086