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Index Register Select: Difference between revisions
From SnesLab
(what REP/SEP might do) |
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In [[emulation mode]], the x flag becomes the [[break flag]]. | In [[emulation mode]], the x flag becomes the [[break flag]]. | ||
There are no BXS or BXC instructions that examine this flag. | |||
=== See Also === | === See Also === | ||
Revision as of 19:09, 4 August 2024
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.
- When set, 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:
In emulation mode, the x flag becomes the break flag.
There are no BXS or BXC instructions that examine this flag.
See Also
References
- Eyes & Lichty, page 422, Table 18.2. 65x Flags. https://archive.org/details/0893037893ProgrammingThe65816/page/422