Integer overflow: Difference between revisions
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Puppydrum64 (talk | contribs) m (→Zilog Z80) |
Puppydrum64 (talk | contribs) m (→Zilog Z80) |
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=={{header|Z80 Assembly}}== |
=={{header|Z80 Assembly}}== |
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===Zilog Z80=== |
===Zilog Z80=== |
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The <code>P</code> flag represents overflow after an arithmetic operation, and bit parity after a bitwise or logical operation. Arithmetic operations will result in overflow if the |
The <code>P</code> flag represents overflow after an arithmetic operation, and bit parity after a bitwise or logical operation. Arithmetic operations will result in overflow if the 0x7F-0x80 boundary is crossed (or in the case of 16-bit math, the 0x7FFF-0x8000 boundary.) One quirk of the Z80 instruction set is that program counter relative jumps cannot be done based on overflow; only calls, returns, and jumps to fixed memory locations are allowed. In other words, the instructions <code>JR PE, label</code> and <code>JR PO, label</code> <i>do not exist.</i> |
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There are no assembler mnemonics for overflow specifically, so we must borrow the ones for parity. |
There are no assembler mnemonics for overflow specifically, so we must borrow the ones for parity. |
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