PM0044 |
STM8 addressing modes |
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6.11Long Pointer Indirect Extended Indexed addressing mode
The pointer address is a word, the pointer size is an extended word, thus allowing 16-Mbyte addressing space, and requires 2 bytes after the op-code.
Example: |
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1089 |
180000 |
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dc.b |
page(table), high(table), low(table) |
180000 |
10203040 table |
dc.b |
$10,$20,$30,$40 |
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1690 |
AE03 |
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LD |
X,#3 |
1692 |
72A71089 |
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LDF |
A,([longptr.e],X) |
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X = 3 |
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A = ([longptr.e],X) = ((longptr.e), X) = (($1089.e), 3)
= ($180000,3) = ($180003) = $40
Doc ID 13590 Rev 3 |
53/162 |
STM8 addressing modes |
PM0044 |
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Figure 20. Long Pointer Indirect Extended Indexed addressing mode example
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Before completion |
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18 |
1089 |
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ptr .word table |
00 |
108A |
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108B |
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PC |
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LDF A,([longptr.w],X) |
72 |
1692 |
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1692 |
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A7 |
1693 |
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10 |
1694 |
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X |
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89 |
1695 |
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03 |
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A |
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Previous value |
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table .byte 0x10,0x20,0x30, |
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180000 |
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0x40 |
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180001 |
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30 |
180002 |
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180000 |
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Adder |
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40 |
180003 |
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Steps to Determine
Effective Address
PC = 1692
PC = PC + 2 = 1694
EA= (((PC) : (PC+1)) : ((PC) : (PC+1) +1) : ((PC) : (PC+1) +2)) + X
EA = 180003
03
EA |
180003 |
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After completion |
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18 |
1089 |
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108A |
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ptr .word table |
00 |
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Instruction Complete |
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00 |
108B |
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X |
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A = (EA) = 40 |
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New PC = PC + 2 = 1696 |
LDF A,([longptr.w],X) |
72 |
1692 |
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A7 |
1693 |
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10 |
1694 |
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89 |
1695 |
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New PC |
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1696 |
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1696 |
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table .byte 0x10,0x20,0x30, |
10 |
180000 |
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0x40 |
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20 |
180001 |
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30 |
180002 |
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A |
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VR02059I |
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40 |
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180003 |
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40 |
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54/162 |
Doc ID 13590 Rev 3 |