
Chapter 4. Floating-Point Unit (FPU)
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4-3
Operand Data Formats and Types
Table 4-2 lists floating-point addressing modes.
4.2 Operand Data Formats and Types
The FPU supports signed byte, word, and longword integer formats, which are identical to
those supported by the integer unit. The FPU also supports single- and double-precision
binary floating-point formats that fully comply with the IEEE-754 standard.
4.2.1 Signed-integer Data Formats
The FPU supports 8-bit byte (B), 16-bit word (W), and 32-bit longword (L) integer data
formats.
4.2.2 Floating-Point Data Formats
Figure 4-1 shows the two binary floating-point data formats.
Figure 4-1. Floating-Point Data Formats
Note that, throughout this chapter, a mantissa is defined as the concatenation of an integer
bit, the binary point, and a fraction. A fraction is the term designating the bits to the right
of the binary point in the mantissa.
Table 4-2. Floating-Point Addressing Modes
Addressing Modes
Syntax
Register direct
Address register direct
Address register direct
Dy
Ay
Register indirect
Address register indirect
Address register indirect with postincrement
Address register indirect with predecrement
Address register indirect with displacement
(Ay)
–(Ay)
(d
16
,Ay)
Program counter indirect with displacement
(d
16
,PC)
11-Bit Exponent
S
52-Bit Fraction
62
51
0
Sign of Mantissa
0
23-Bit Fraction
8-Bit Exponent
S
Sign of Mantissa
22
30
Single
Double
31
63
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