Even or odd: Difference between revisions
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A right rotate will set the carry if the register's value is odd and clear it if it's even. This does alter the contents of the register, so only use this method if you don't need to remember the number being tested after getting the results of the test. This is the fastest way the Z80 can test a value for even or odd, but only when testing the accumulator <tt>A</tt> |
A right rotate will set the carry if the register's value is odd and clear it if it's even. This does alter the contents of the register, so only use this method if you don't need to remember the number being tested after getting the results of the test. This is the fastest way the Z80 can test a value for even or odd, but only when testing the accumulator <tt>A</tt> |
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<syntaxhighlight lang="z80">rrca |
<syntaxhighlight lang="z80">rrca |
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jp nc,isEven</syntaxhighlight> |
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===SRA/SRL=== |
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In similar vein, there are also shift instructions. The arithmetic shift instruction retains the sign bit (bit 7) of the operand in question, while the logical shift sets bit 7 to 0. |
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<syntaxhighlight lang="z80">sra a |
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jp nc,isEven</syntaxhighlight> |
jp nc,isEven</syntaxhighlight> |
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