Instruction Overview
18-16
ADSP-BF53x/BF56x Blackfin Processor Programming Reference
The Quad 8-Bit Add instruction provides byte alignment directly in the
source register pairs
src_reg_0
and
src_reg_1
based on index registers
I0
and
I1
.
• The two LSBs of the
I0
register determine the byte alignment for
source register pair
src_reg_0
(typically
R1:0
).
• The two LSBs of the
I1
register determine the byte alignment for
source register pair
src_reg_1
(typically
R3:2
).
The relationship between the I-register bits and the byte alignment is
illustrated below.
In the default source order case (for example, not the (R) syntax), assume
that a source register pair contains the data shown in
Table 18-9
.
This instruction prevents exceptions that would otherwise be caused by
misaligned 32-bit memory loads issued in parallel.
Options
The (R) syntax reverses the order of the source registers within each regis-
ter pair. Typical high performance applications cannot afford the
overhead of reloading both register pair operands to maintain byte order
Table 18-7. Source Registers Contain
31................24
23................16
15..................8
7....................0
aligned_src_reg_0:
y3
y2
y1
y0
aligned_src_reg_1:
z3
z2
z1
z0
Table 18-8. Destination Registers Receive
31................24
23................16
15..................8
7....................0
aligned_src_reg_0:
y1 + z1
y0 + z0
aligned_src_reg_1:
y3 + z3
y2 + z2
Содержание ADSP-BF53x Blackfin
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Страница 742: ...Instruction Overview 19 54 ADSP BF53x BF56x Blackfin Processor Programming Reference...
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...