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Rev. 5.00, 09/03, page 28 of 760
2.3.2 Addressing Modes
Addressing modes and effective address calculation methods are shown in table 2.2.
Table 2.2 Addressing Modes and Effective Addresses
Addressing
Mode
Instruction
Format Effective Address Calculation Method Calculation Formula
Register direct Rn
Effective address is register Rn. (Operand is
register Rn contents.)
—
Register
indirect
@Rn Effective address is register Rn contents.
Rn Rn
Rn
Register
indirect with
post-increment
@Rn+ Effective address is register Rn contents. A
constant is added to Rn after instruction
execution: 1 for a byte operand, 2 for a word
operand, 4 for a longword operand.
Rn
Rn
1/2/4
+
Rn + 1/2/4
Rn
After instruction
execution
Byte: Rn + 1 → Rn
Word: Rn + 2 → Rn
Longword: Rn + 4 → Rn
Register
indirect with
pre-decrement
@–Rn Effective address is register Rn contents,
decremented by a constant beforehand: 1 for
a byte operand, 2 for a word operand, 4 for a
longword operand.
Rn
1/2/4
Rn − 1/2/4
−
Rn − 1/2/4
Byte: Rn – 1 → Rn
Word: Rn – 2 → Rn
Longword: Rn – 4 → Rn
(Instruction executed
with Rn after
calculation)