dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 206

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

Address Generation Unit
After the code in Example 6-3 on page 6-11 is executed, the accumulators hold the following values:
Note that the last instruction in Example 6-3, which loads the long-word variable into D, specifies an offset
value of two. This value is specified because constant offsets for both word and long-word memory
accesses are always specified in words. The operation performed by the
is shown in Figure 6-5.
Note that, for instructions that move bytes, the offset is specified in the number of bytes, whereas, for word
and long instructions, the offset is specified in the number of words. Also note that accesses to bytes in the
data structure in Example 6-3 on page 6-11 require the MOVE.B and MOVEU.B instructions instead of
MOVE.BP and MOVEU.BP. This requirement exists because the R3 register is used as a word pointer.
6-12
A
B
C
D
D
X
X
X
X
X
$7004
$7003
$7002
$7001
$7000
M01
R3
N
Figure 6-5. Executing the MOVE.L X:(R3+2),D Instruction
15
Before Execution
Before Execution
$DD
$BB
X
X
X
X
X
X Memory
$FFFF
$FFFF
$1234
$5678
$7000
$9876
$CC
from the Instruction Word
$AA
Short Immediate Value
DSP56800E Core Reference Manual
0
<< 1
X
X
X
X
X
+
A
B
C
D
D
$F
$0
$F
$0
$0
$7004
$7003
$7002
$7001
$7000
M01
R3
N
15
$FFBB
$00CC
$FFFF
MOVE.L X:(R3+2),D
After Execution
$1234
After Execution
$1234
$DD
$BB
X Memory
$FFFF
$FFFF
$1234
$5678
$7000
$9876
$CC
$AA
Freescale Semiconductor
0
$0000
$0000
$0000
$5678
$5678
Word
Long
4 Bytes
instruction