Freescale Semiconductor MCF5480 - Manual (Page 122)

MCF548x Reference Manual, Rev. 3
3-18 Freescale Semiconductor
3.4.2.1.1 Signed-Integer Data Formats
The FPU supports 8-bit byte (B), 16-bit word (W), and 32-bit longword (L) integer data formats.
3.4.2.1.2 Floating-Point Data Formats
Figure 3-13 shows the two binary floating-point data formats.
Figure 3-13. 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.
Figure 3-14. Mantissa
The integer bit is implied to be set for normalized numbers and infinities, clear for zeros and denormalized
numbers. For not-a-numbers (NANs), the integer bit is ignored. The exponent in both floating-point
formats is an unsigned binary integer with an implied bias added to it. Subtracting the bias from exponent
yields a signed, two’s complement power of two. This represents the magnitude of a normalized
floating-point number when multiplied by the mantissa.
By definition, a normalized mantissa always takes values starting from 1.0 and going up to, but not
including, 2.0; that is, [1.0...2.0).
3.5 Addressing Mode Summary
Addressing modes are categorized by how they are used. Data addressing modes refer to data operands.
Memory addressing modes refer to memory operands. Alterable addressing modes refer to alterable
(writable) data operands. Control addressing modes refer to memory operands without an associated size.
These categories sometimes combine to form more restrictive categories. Two combined classifications
are alterable memory (both alterable and memory) and data alterable (both alterable and data). Twelve of
the most commonly used effective addressing modes from the M68000 Family are available on ColdFire
microprocessors. Table 3-6 summarizes these modes and their categories.
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
(integer bit).(fraction)
Mantissa