dsp56800 Freescale Semiconductor, Inc, dsp56800 Datasheet - Page 95

• Manufacturer Part Number: dsp56800
• Description: 16-bit Digital Signal Controllers
• Manufacturer: Freescale Semiconductor, Inc

4.2.2.6
This addressing mode contains the 6-bit short immediate index within the instruction word. This field is
always one-extended to form a negative offset when the SP register is used and is always zero-extended to
form a positive offset when the R2 register is used. The type of arithmetic used to add the short
displacement to R2 or SP is always linear; modulo arithmetic is not allowed. This addressing mode
requires an extra instruction cycle. This reference is classified as an X memory reference. See Figure 4-8.
Freescale Semiconductor
Assembler syntax: X:(R2+xx), X:(SP-xx)
Additional instruction execution cycles: 1
Additional effective address program words: 0
A
35 32 31
Index by Short Displacement: (SP-xx), (R2+xx)
A2
F
$7003
$7000
M01
R2
E
Figure 4-8. Address Register Indirect: Indexed by Short Displacement
N
Before Execution
15
15
15
15
D
X
X
Indexed by Short Displacement Example
A1
X Memory
$FFFF
$7000
$4567
C
X
X
from the Instruction Word
Short Immediate Value
B
16 15
X
X
X
X
A
0
0
0
0
9
A0
Address Generation Unit
+
8
7
0
A
35 32 31
A2
: MOVE A1,X:(R2+3)
F
$7003
$7000
M01
R2
E
N
15
15
15
15
After Execution
D
E
X
A1
X Memory
$FFFF
$7000
$4567
C
D
X
B
16 15
C
X
B
X
A
0
0
0
0
9
Addressing Modes
A0
8
7
0
AA0021
4-15