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Rabbit 4000 cbm instruction - (de) operand without ioi or ioe?

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The description of the Rabbit 4000 cbm instruction states calls (de) "address of I/O register" and states "only (de) is affected by ioi or ioe".

What happens if neither ioi or ioe is used? What will (de) refer to? Internal I/O? External I/O? Memory?

If the latter, will the instruction work normally for (de) == (hl)?

If yes, it could be very useful for setting or resetting bits in memory, in particular for implementing bitfields.

Philipp
asked Nov 7, 2020 in Rabbit by spth New to the Community (24 points)

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Experimentally, using an RCM 4110, despite all the wording about "I/O register" in the documentation, the instruction actually just works normally with memory operands like any other instruction.
answered Nov 28, 2020 by spth New to the Community (24 points)
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