Memory/Accumulator Select

The Memory/Accumulator Select (M) flag exists in the processor status register (bit 5) of the 65c816. It indicates whether the accumulator is 8 or 16 bits wide:

• When clear, the accumulator is 16 bits wide.
• When set, the accumulator is 8 bits wide, but the high byte (B) is still retained.

It can be affected by:

• REP
• SEP
• PLP
• RTI

This flag is only relevant in native mode.

See Also

• Index Register Select

Reference

• Eyes & Lichty, page 422, Table 18.2. 65x Flags. https://archive.org/details/0893037893ProgrammingThe65816/page/422