Index By Long Displacement: (Rn+Xxxx), (Sp+Xxxx); Figure 4-9 Address Register Indirect: Indexed By Long Displacement - Motorola DSP56800 Manual

Address Generation Unit
4.2.2.7

Index by Long Displacement: (Rn+xxxx), (SP+xxxx)

This addressing mode contains the 16-bit long immediate index within the instruction word. This second
word is treated as a signed two's-complement value. The type of arithmetic (linear or modulo) used to add
the long displacement to Rn is determined by M01 for R0 and R1 and is always linear for R2, R3, and SP.
This addressing mode requires two extra instruction cycles. This addressing mode is available for MOVEC
instructions. This reference is classified as an X memory reference. See Figure 4-9.
Indexed by Long Displacement Example
Before Execution
A2 A1
A F E D
35 32 31
15
$80CF X
$7000 X
R0
15
N
15
M01
15
Assembler syntax: X:(Rn+xxxx), X:(SP+xxxx)
Additional instruction execution cycles: 2
Additional effective address program words: 1
Figure 4-9. Address Register Indirect: Indexed by Long Displacement
4-16
A0
C B A 9 8 7
16 15 0
X Memory
0
X X X
X X X
$7000
0
+
$4567
0
$FFFF
0
Long Immediate Value
from the Instruction Word
DSP56800 Family Manual
: MOVE A1,X:(R0+$10CF)
After Execution
A2 A1
A F E D C B
35 32 31 16 15
X Memory
15
$80CF E D C
$7000 X X X
R0 $7000
15
N $4567
15
M01 $FFFF
15
A0
A 9 8 7
0
0
B
X
0
0
0
AA0022