Data Organization and Addressing Capabilities
MOTOROLA MC68030 USER’S MANUAL 2-23
Field Definition Field Definition
Instruction: BS Base Register Suppress:
Register General Register Number 0 = Base Register Added
Extensions: 1 = Base Register Suppressed
Register Index Register Number IS Index Suppress:
D/A Index Register Type 0 = Evaluate and Add Index
0 = Dn Operand
1 = An 1 = Suppress Index Operand
W/L Word/Long-Word Index Size BD SIZE Base Displacement Size:
0 = Sign-Extended Word 00 = Reserved
1 = Long Word 01 = Null Displacement
Scale Scale Factor 10 = Word Displacement
00 =1 11 Long Displacement
01 =2 I/IS Index/Indirect Selection
10 = 4 Indirect and Indexing Operand
11 = 8 Determined in Conjunction with
Bit 6, Index Suppress
Figure 2-4. Effective Address Specification Formats
Effective address modes are grouped according to the use of the mode. They can be
classified as follows:
Data A data addressing effective address mode is one that refers to data operands.
Memory A memory addressing effective address mode is one that refers to memory
operands.
Alterable An alterable addressing effective address mode is one that refers to alterable
(writable) operands.
Control A control addressing effective address mode is one that refers to memory
operands without an associated size.
Single Effective Address Instruction Format
15 14 13 12 11 10 9 8 7 6 5 0
X X X X X X X X X X
EFFECTIVE ADDRESS
MODE REGISTER
Brief Format Extension Word
15 14 12 11 10 9 8 7 0
D/A REGISTER W/L SCALE 0 DISPLACEMENT
Full Format Extension Word(s)
15 14 12111098765432 0
D/A REGISTER W/L SCALE 1 BS IS BD SIZE 0 I/IS
BASE DISPLACEMENT (0, 1, OR 2 WORDS)
OUTER DISPLACEMENT (0, 1, OR 2 WORDS)
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