Motorola MC68030 User Manual page 74

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2-28
The outer displacement (od) available in the memory indirect modes is added
to the pointer in memory. The syntax for these modes is ([bd,Anl,Xn,od) and
([bd,An,Xnl,od). When the pointer is the address of a structure in memory
and the outer displacement is the offset of an item in the structure, the
memory indirect modes can access the item efficiently (refer to Figure 2-9).
Memory indirect addressing modes are used with a base displacement in
five basic forms:
1. [bd,An] - Indirect, suppressed index register
2. ([bd,An,Xn]) - Preindexed indirect
3. ([bd,Anl,Xn) - Postindexed indirect
4. ([bd,An,Xnl,od) - Preindexed indirect with outer displacement
5. ([bd,Anl,Xn,od) - Postindexed indirect with outer displacement
SYNTAX: ([bd))
bd
POINTER DATA ITEM
' 7 ' 7
7 7
Figure 2-8. Using Indirect Absolute Memory Addressing
SYNTAX: ([Anl.ad)
MEMORY
STRUCTURE
An
POINTER
ad
DATA ITEM
' 7 ' 7 ' 7 ' 7
Figure 2-9. Accessing an Item in a Structure Using Pointer
MC68030 USER'S MANUAL
MOTOROLA