dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 56

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

Data Types and Addressing Modes
3.2.1
The 16-bit DSC core supports four types of two’s-complement data formats:
Signed and unsigned integer data types are useful for general-purpose computing; they are familiar to
microprocessor and microcontroller programmers. Fractional data types allow for powerful numeric and
digital-signal-processing algorithms to be implemented.
3.2.1.1
This format is used for processing data as integers. In this format, the N-bit operand is represented using
the N.0 format (N integer bits). Signed integer numbers lie in the following range:
This data format is available for bytes, words, and longs. The most negative, signed word that can be
represented is –32,768 ($8000), and the most negative, signed long word is –2,147,483,648 ($80000000).
The most positive signed word is 32,767 ($7FFF), and the most positive signed long word is 2,147,483,647
($7FFFFFFF).
3.2.1.2
Unsigned integer numbers are positive only, and they have nearly twice the magnitude of a signed number
of the same size. Unsigned integer numbers lie in the following range:
The binary word is interpreted as having a binary point immediately to the right of the integer’s least
significant bit.
This data format is available for bytes, words, and long words. The most positive, 16-bit, unsigned integer
is 65,535 ($FFFF), and the most positive, 32-bit, unsigned integer is 4,294,967,295 ($FFFFFFFF). The
smallest unsigned integer number is zero ($0000), regardless of size.
3.2.1.3
In this format, the N bit operand is represented using the 1.[N–1] format (1 sign bit, N–1 fractional bits).
Signed fractional numbers lie in the following range:
This data format is available for words and long words. For both word and long-word signed fractions, the
most negative number that can be represented is –1.0, whose internal representation is $8000 (word) or
$80000000 (long word). The most positive word is $7FFF (1.0 – 2
$7FFFFFFF (1.0 – 2
3-6
•
•
•
•
Signed integer
Unsigned integer
Signed fractional
Unsigned fractional
–2
0 ≤ UI ≤ [2
–1.0 ≤ SF ≤ +1.0 – 2
Data Formats
[N–1]
Signed Integer
Unsigned Integer
Signed Fractional
≤ SI ≤ [2
N
–31
– 1]
).
[N–1]
–[N–1]
– 1]
DSP56800E Core Reference Manual
–15
), and the most positive long word is
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