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SINGLE EA INSTRUCTION FORMAT
15
14
13
12
11
10
9
8
7
6
5
4
3
2
o
EFFECTIVE ADDRESS
X
X
X
X
X
X
X
X
X
X
MODE
I
REGISTER
BRIEF FORMAT EXTENSION WORD
15
14
12
11
10
9
8
7
o
lOlA
I
REGISTER
I
WIL
I
SCALE
I
0
I
DISPLACEMENT
FULL FORMAT EXTENSION WORD(S)
15
14
12
11
10
9
8
7
6
4
3
2
0
REGISTER
Field
Instruction
Register
Extension
Register
DIA
WIL
Scale
Definition
Field
BS
General Register Number
Index Register Number
IS
Index Register Type
O=Dn
1 =An
BD SIZE
WordlLong Word Index Size
0= Sign-Extended Word
1
=
Long Word
Scale Factor
00
=
1
IllS *
01 =2
10
=
4
11
=
8
IllS
Definition
Base Register Suppress
0= Base Register Added
1 = Base Register Suppressed
Index Suppress
o
= Evaluate and Add Index Operand
1 = Suppress Index Operand
Base Displacement Size
00 = Reserved
01 = Null Displacement
10 = Word Displacement
11 = Long-Word Displacement
Indexllndirect Selection
Indirect and Indexing Operand
Determined in Conjunction with Bit 6,
Index Suppress
*Memory indirect addressing will cause illegal instruction trap; must be = 000 if IS
=
1
Figure 3-2. Effective Address Specification Formats
EA modes can be classified as follows:
Data
A data addressing EA mode refers to data operands.
Memory A memory addressing EA mode refers to memory operands.
Alterable An alterable addressing EA mode refers to writable operands.
Control
A control addressing EA mode refers to unsized memory operands
Categories are sometimes combined, forming new, more restrictive, categories.
Two examples are alterable memory or alterable data. The former refers to
addressing modes that are both alterable and memory addresses; the latter
refers to addressing modes that are both alterable and data addresses. Table
3-1 shows categories to which each of the EA modes belong.
CPU32 REFERENCE MANUAL
DATA ORGANIZATION AND
ADDRESSING CAPABILITIES
MOTOROLA
3-13
III
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