Chapter 1. Introduction
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1-11
Data Format Summary
1.7.2 EMAC Data Representation
The EMAC supports the following three modes, where each mode defines a unique operand
type.
Two’s complement signed integer: In this format, an N-bit operand value lies in the
range -2
(N-1)
< operand < 2
(N-1)
- 1. The binary point is right of the lsb.
Unsigned integer: In this format, an N-bit operand value lies in the range 0 < operand
< 2
N
- 1. The binary point is right of the lsb.
Two’s complement, signed fractional: In an N-bit number, the first bit is the sign bit.
The remaining bits signify the first N-1 bits after the binary point. Given an N-bit
number,
a
N-1
a
N-2
a
N-3
... a
2
a
1
a
0
, its value is given by the equation in Figure 1-7.
Figure 1-7. Two’s Complement, Signed Fractional Equation
This format can represent numbers in the range -1 < operand < 1 - 2
(N-1)
.
For words and longwords, the largest negative number that can be represented is -1, whose
internal representation is 0x8000 and 0x8000_0000, respectively. The largest positive word
is 0x7FFF or (1 - 2
-15
); the most positive longword is 0x7FFF_FFFF or (1 - 2
-31
).
For more information, see Chapter 5, “Enhanced Multiply-Accumulate Unit (EMAC).”
1.7.2.1 Floating-Point 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.
31
24 23
16 15
8
7
0
Longword 0x0000_0000
Word 0x0000_0000
Word 0x0000_0002
Byte 0x0000_0000
Byte 0x0000_0001
Byte 0x0000_0002
Byte 0x0000_0003
Longword 0x0000_0004
Word 0x0000_0004
Word 0x0000_0006
Byte 0x0000_0004
Byte 0x0000_0005
Byte 0x0000_0006
Byte 0x0000_0007
.
.
.
.
.
.
.
.
.
Word 0xFFFF_FFFC
Word 0xFFFF_FFFE
Byte 0xFFFF_FFFC
Byte 0xFFFF_FFFD
Figure 1-6. Memory Operand Addressing
Byte 0xFFFF_FFFE
Byte 0xFFFF_FFFF
value
1 a
N
1
–
(
)
–
2
i
1
N
–
+
(
)
ai
i
0
=
N
2
–
∑
+
=
F
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n
.