Freescale Semiconductor StarCore SC140 - Manual (Page 51)

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
39
– 1 represented by
$7F FFFF FFFF. The most negative number is –2
39
, represented by $80 0000 0000.
2.2.2.2.3 Unsigned Integer
Unsigned integer numbers may be thought of as positive only. The unsigned numbers have nearly twice
the magnitude of a signed number of the same length. Unsigned integer numbers lie in the following range:
0
≤
UI
≤
[2
N
-1]
The binary word is interpreted as having a binary point immediately to the right of the LSB. The most
positive 16-bit unsigned integer is 65535 ($FFFF). The most positive 32-bit unsigned integer is 2
32
-1
($FFFF FFFF). The smallest unsigned number is zero ($0000).
If the extension bits are in use, the range is from zero to +2
40
– 1.
Table 2-12. Two’s Complement Word Representations
Signed Fractional Signed Integer Unsigned Integer
$7FFF $7FFF $FFFF
l l l l $FFFE
l l l l l l
$0001 $0001 +1 l l
$0000 0 $0000 0 l l
$FFFF $FFFF l l
l l l l l l
l l l l $0001 1
$8000 $8000 $0000 0
1.0 2 15 – – 2 15 1 – 2 16 1 –
2 16 2 –
2 15 –
2 15 – – 1 –
1.0 – 2 15 –