Section 6 Floating-Point Unit; Overview; Data Formats; Floating-Point Format - Hitachi SH7751 Hardware Manual

6.1

Overview

The floating-point unit (FPU) has the following features:


Conforms to IEEE754 standard


32 single-precision floating-point registers (can also be referenced as 16 double-precision
registers)


Two rounding modes: Round to Nearest and Round to Zero


Two denormalization modes: Flush to Zero and Treat Denormalized Number


Six exception sources: FPU Error, Invalid Operation, Divide By Zero, Overflow, Underflow,
and Inexact


Comprehensive instructions: Single-precision, double-precision, graphics support, system
control
When the FD bit in SR is set to 1, the FPU cannot be used, and an attempt to execute an FPU
instruction will cause an FPU disable exception.
6.2

Data Formats

6.2.1

Floating-Point Format

A floating-point number consists of the following three fields:


Sign (s)


Exponent (e)


Fraction (f)
The SH7751 Series can handle single-precision and double-precision floating-point numbers,
using the formats shown in figures 6.1 and 6.2.
31 30
s

Figure 6.1 Format of Single-Precision Floating-Point Number

Section 6 Floating-Point Unit

23 22
e f
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