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Index Register Select

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Revision as of 15:31, 16 August 2024 by Xetheria (talk | contribs) (8 bits wide in emulation mode)
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Index Register Select (X) is a flag in the processor status register (bit 4) of the 65c816. It indicates how wide the index registers are:

  • When clear, both index registers are 16 bits wide. It can only be clear in native mode.
  • When set or in emulation mode, both index registers are 8 bits wide.

It is not possible to control the width of the two index registers individually.

It can be affected by:

It affects the behavior of (incomplete list):

In emulation mode, the x flag becomes the break flag.

There are no BXS or BXC instructions that examine this flag.

See Also

Reference