ADSP-BF53x/BF56x Blackfin Processor Programming Reference
19-25
Vector Operations
“ASHIFT” Syntax
Both half-word registers in
src_reg
are shifted by the number of places
prescribed in
shift_magnitude
, and the result stored into
dest_reg
.
The sign of the shift magnitude determines the direction of the shift for
the
ASHIFT
versions.
• Positive shift magnitudes without the saturation flag ( – , S) pro-
duce Logical Left shifts.
• Positive shift magnitudes with the saturation flag ( – , S) produce
Arithmetic Left shifts.
• Negative shift magnitudes produce Arithmetic Right shifts.
In essence, the magnitude is the power of 2 multiplied by the
src_reg
number. Positive magnitudes cause multiplication ( N x 2
n
), whereas neg-
ative magnitudes produce division ( N x 2
-n
or N / 2
n
).
The
dest_reg
and
src_reg
are both pairs of 16-bit half registers. Satura-
tion of the result is optional.
Valid shift magnitudes for 16-bit
src_reg
are –16 t15, zero
included. If a number larger than these is supplied, the instruction masks
and ignores the more significant bits.
This instruction does not implicitly modify the
src_reg
values. Option-
ally,
dest_reg
can be the same D-register as
src_reg
. Using the same
D-register for the
dest_reg
and the
src_reg
explicitly modifies the source
register.
Options
The
ASHIFT
instruction supports the ( – , S) option, which saturates the
result.
Содержание ADSP-BF53x Blackfin
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Страница 752: ...Examples 20 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 780: ...Product Identification Register 21 28 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 790: ...ADSP BF535 Flags A 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 800: ...Performance Monitor Registers B 10 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 994: ...Instructions Listed By Operation Code C 194 ADSP BF53x BF56x Blackfin Processor Programming Reference...
Страница 1042: ...Index I 40 ADSP BF53x BF56x Blackfin Processor Programming Reference...