dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 57

• Manufacturer Part Number: dsp56800e
• Description: 16-bit Digital Signal Controller Core
• Manufacturer: Freescale Semiconductor, Inc

3.2.1.4
Unsigned fractional numbers may be thought of as positive only, and they have nearly twice the magnitude
of a signed number with the same number of bits. Unsigned fractional numbers lie in the following range:
The binary word is interpreted as having a binary point after the MSB.
This data format is available for words and longs. The most positive, 16-bit, unsigned number is $FFFF, or
{1.0 + (1.0 – 2
3.2.2
Data in a memory location or register can be interpreted as fractional or integer, depending on a program’s
needs. Table 3-2 shows how a 16-bit value can be interpreted as either fractional or integer, depending on
the location of the binary point.
The relationship between the integer interpretation of a 16-bit value and the corresponding fractional
interpretation is:
There is a similar relationship between 32-bit integers and fractional values:
Table 3-3 on page 3-8 shows how a 36-bit value can be interpreted as either an integer or fractional value,
depending on the location of the binary point.
Freescale Semiconductor
Representation
Hexadecimal
$7FFF
$C000
$E000
$F000
$7000
$4000
$2000
$1000
$0000
$9000
$8000
0.0 ≤ UF ≤ 2.0 – 2
Fractional Value = Integer Value / (2
Fractional Value = Integer Value / (2
Understanding Fractional and Integer Data
Unsigned Fractional
– [N–1]
)} = 1.99997. The smallest unsigned fractional number is zero ($0000).
0111 1111 1111 1111.
0111 0000 0000 0000.
0100 0000 0000 0000.
0010 0000 0000 0000.
0001 0000 0000 0000.
0000 0000 0000 0000.
1100 0000 0000 0000.
1110 0000 0000 0000.
1111 0000 0000 0000.
1001 0000 0000 0000.
1000 0000 0000 0000.
–[N–1]
Table 3-2. Interpretation of 16-Bit Data Values
Binary
Data Types and Addressing Modes
Integer
15
31
)
)
Decimal
–16384
–28672
–32768
32767
28672
16384
–8192
–4096
8192
4096
0
0.111 1111 1111 1111
0.111 0000 0000 0000
0.100 0000 0000 0000
0.010 0000 0000 0000
0.001 0000 0000 0000
0.000 0000 0000 0000
1.100 0000 0000 0000
1.110 0000 0000 0000
1.111 0000 0000 0000
1.001 0000 0000 0000
1.000 0000 0000 0000
Binary
Fraction
DSP56800E Data Types
Decimal
0.99997
–0.125
–0.875
0.875
0.125
–0.25
0.25
–0.5
–1.0
0.5
0.0
3-7