Re: [f-cpu] Supported Instructions

[Juergen Goeritz <goeritz@oekomm.de>]

On Sun, 7 Apr 2002, Christophe wrote:
>> Do you think this is a good idea? IMO then you need to know
>> (i.e. implement) about parts of the opcode already. The
>> best method would be to just treat it as 'unknown' and
>> let the emulation take control. In that case you are also
>> free to add opcodes later that have not been thought of
>> today, e.g. additional application specific opcodes that
>> may only be implemented in few members of the f-cpu family
>> or offsprings.
>
>In fact, whatever is the opcode, F-CPU just extracts the three fields and give
>us their contents. The opcode could never use one or two of those registers
>(one or two operands instructions) so it doesn't make a difference. It is the
>software to do whatever it wants with this info. So F-CPU really lets the
>emulation take control, because it is only the emulation code which knows what
>to do with. Such a feature could be disabled or better thought.

My idea is to implement nothing at all for unimplemented
opcodes to be free for future changes. And unimplemented
opcodes should always generate an exception.

>> With f-cpu I would wish for such free opcode blocks just
>> to be able to add e.g. special opcodes for grafical use
>> when f-cpu is controlling a 3D grafic human interface in
>> the future. Keep it free to be extendable even in ways
>> that may not be very common today but may get very much
>> wanted in the next 30 years (didn't YG intended that?).
>
>Do such free opcode blocks trigger an exception anyhow ?

Häh? What else? Any unimplemented opcode should trigger
an exception. Otherwise it would be implemented. Shrug,
maybe I didn't quite understand your question?

JG

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