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Section 2 CPU
Rev. 4.00 Sep. 14, 2005 Page 48 of 982
REJ09B0023-0400
2.4 Instruction Formats
2.4.1 CPU Instruction Addressing Modes
The following table shows addressing modes and effective address calculation methods for
instructions executed by the CPU core.
Table 2.11 Addressing Modes and Effective Addresses for CPU Instructions
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. It is
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)