PM0044 |
STM8 addressing modes |
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6.4.4Long Indexed addressing mode
The offset is a word, thus allowing up to 128 KB addressing space, but requires 2 bytes after the op-code.
Example: |
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0690 |
AE02 |
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LD |
X,#2 |
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0692 |
D6077E |
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LD |
A,(table,X) |
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077E |
BF |
table |
dc.b |
$BF |
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86 |
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dc.b |
$86 |
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DBCF |
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dc.w $DBCF |
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Action:
X = 2
A = (table, X) = ($077E, X) = ($077E, 2) = ($0780) = $DB
Figure 14. Long Indexed - 16-bit offset - addressing mode example
Before completion
LD A, (table, X)
table . byte BF
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PC |
D6 |
0692 |
0692 |
07 |
0693 |
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7E |
0694 |
X |
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02 |
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077E |
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BF |
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A |
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86 |
077F |
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Previous Value |
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DB |
0780 |
077E |
02 |
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CF |
0781 |
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Adder |
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Steps to Determine Effective Address
PC = 0692
PC = PC + 1 = 0693 EA = (PC):(PC+1) + X
= 077E + 02 = 0780
EA 0780
After Completion
LD A, (table, X)
table . byte BF
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X |
Instruction Complete |
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D6 |
0692 |
02 |
A = (EA) = DB |
07 |
0693 |
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New PC = PC + 2 = 0695 |
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7E |
0694 |
New PC |
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0695 |
0695 |
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BF |
077E |
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86 |
077F |
A |
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DB |
0780 |
DB |
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CF |
0781 |
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VR02059E |
Doc ID 13590 Rev 3 |
43/162 |