Freescale-semiconductor StarCore SC140 Manual de usuario descargar pdf (Pagina 51)

100

101

DALU

SC140 DSP Core Reference Manual 2-19

2.2.2.2.2 Signed Integer

This format is used when processing data as integers. Using this format, the N-bit operand is represented

using the N.0 bit format (N integer bits). Signed integer numbers lie in the following range:

-2

[N-1]

≤

SI ≤ [2

[N-1]

-1]

For words and long-word signed integers, the most negative word that can be represented is -32768

($8000) and the most negative long word is -2147483648 ($8000 0000). The most positive word is 32767

($7FFF) and the most positive long word is 2147483647 ($7FFF FFFF).

If the extension bits are in use, N becomes 40, and the most positive number is 2

– 1 represented by

$7F FFFF FFFF. The most negative number is –2

, represented by $80 0000 0000.

2.2.2.2.3 Unsigned Integer

Unsigned integer numbers may be thought of as positive only. The unsigned numbers have nearly twice

the magnitude of a signed number of the same length. Unsigned integer numbers lie in the following range:

≤ UI ≤ [2

-1]

The binary word is interpreted as having a binary point immediately to the right of the LSB. The most

positive 16-bit unsigned integer is 65535 ($FFFF). The most positive 32-bit unsigned integer is 2

-1

($FFFF FFFF). The smallest unsigned number is zero ($0000).

If the extension bits are in use, the range is from zero to +2

– 1.

Table 2-12. Two’s Complement Word Representations

Signed Fractional Signed Integer Unsigned Integer

$7FFF $7FFF $FFFF

llll$FFFE

llllll

$0001 $0001 +1 l l

$0000 0 $0000 0 l l

$FFFF $FFFF l l

llllll

llll$00011

$8000 $8000 $0000 0

1.0 2

15–

–2

1–2

1–

2–

15–

–

1–

1.0–

–

1 2 ... 46 47 48 49 50 51 52 53 54 55 56 ... 759 760

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Freescale-semiconductor StarCore SC140 Manual de usuario Pagina 51

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