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three_or_more_pass_assembly
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This shows you the differences between two versions of the page.
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three_or_more_pass_assembly [2021/09/19 15:53] richardrussell created |
three_or_more_pass_assembly [2021/09/19 15:57] (current) richardrussell |
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| - | But wait, this is wrong! The address of test% is **&09A31DB9** but the value pushed in the previous instruction is **&09A31DB6**. BBC BASIC is broken! I want my money back! | + | But wait, this is wrong! The address test% is **&09A31DB9** but the value pushed in the previous instruction is **&09A31DB6**. BBC BASIC is broken! I want my money back! |
| No, it's not broken. On the first pass the value of test% is **zero**, because it's declared as LOCAL, so the assembler encodes the 'push 0' as 6A 00. But on the second pass the value of test% is no longer in the range -128 to +127 and therefore the assembler uses the long encoding: 68 B6 1D A3 09. The resulting phase error causes the code emitted by the assembler to be invalid. | No, it's not broken. On the first pass the value of test% is **zero**, because it's declared as LOCAL, so the assembler encodes the 'push 0' as 6A 00. But on the second pass the value of test% is no longer in the range -128 to +127 and therefore the assembler uses the long encoding: 68 B6 1D A3 09. The resulting phase error causes the code emitted by the assembler to be invalid. | ||
three_or_more_pass_assembly.txt ยท Last modified: 2021/09/19 15:57 by richardrussell
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