At 16:37 1/20/00 +0100, you wrote:
>>Would it then be possible to write a game that flips back and forth between
>>7800 and 2600 mode, maintaining state?
>
>That would be very difficult, since the register that controls the
>state of the RAM, ROM and graphics chip can be accessed by writing to the
>low nibble of all addresses between $00 and $1F. Since that overlaps
>with many TIA registers (of which only the sound registers are used
>in MARIA mode), you would have to be very carefull that you don't
>accidentally change the state of something that your code relies on.
>Therefore it's better to choose one setting and lock that in.
Not to mention you only get two writes to the control register! After 2
writes, it halts the processor!! There are two chained flipflops that
shift a "1" through each bit, and on the third write to the control register,
the last output goes high, which runs thru a transistor to the processor's
HALT line, stopping the processor.
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