Datasheet

52
2.3.2 Addressing Modes
Table 2.8 describes addressing modes and effective address calculation.
Table 2.8 Addressing Modes and Effective Addresses
Addressing
Mode
Instruction
Format Effective Addresses Calculation Equation
Direct register
addressing
Rn The effective address is register Rn. (The operand
is the contents of register Rn.)
Indirect register
addressing
@Rn The effective address is the content of register Rn.
Rn Rn
Rn
Post-increment
indirect register
addressing
@Rn+ The effective address is the content of register Rn.
A constant is added to the content of Rn after the
instruction is executed. 1 is added for a byte
operation, 2 for a word operation, and 4 for a
longword operation.
Rn Rn
1/2/4
+
Rn + 1/2/4
Rn
(After the
instruction
executes)
Byte: Rn + 1
Rn
Word: Rn + 2
Rn
Longword:
Rn + 4 Rn
Pre-decrement
indirect register
addressing
@–Rn The effective address is the value obtained by
subtracting a constant from Rn. 1 is subtracted for
a byte operation, 2 for a word operation, and 4 for
a longword operation.
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)