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mg_notes:iie_card:weird_stuff [2018/12/21 17:48] M.G. [Weird Beep] |
mg_notes:iie_card:weird_stuff [2019/08/14 15:22] (current) M.G. [LC //e Card - Weird Stuff] |
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| - | ====== LC //e Card - Weird Stuff ====== | + | ====== LC //e Card - Weird Stuff: Opcode $02 ====== |
| ===== Weird Beep ===== | ===== Weird Beep ===== | ||
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| The $02 $03 sequence behaves as if CMP #$C0 or CMP #$Cn-1 has been executed and if it has, displays "UNABLE TO BOOT FROM STARTUP SLOT" in the center of the screen in a similar manner to the copyright message. The message is not in Apple II memory. It returns with the flags set as executing the CMP instruction would have. | The $02 $03 sequence behaves as if CMP #$C0 or CMP #$Cn-1 has been executed and if it has, displays "UNABLE TO BOOT FROM STARTUP SLOT" in the center of the screen in a similar manner to the copyright message. The message is not in Apple II memory. It returns with the flags set as executing the CMP instruction would have. | ||
| + | My ''iie.card'' [[https://github.com/mgcaret/davex-mg-utils/blob/master/iie.card.s|utility]] for Davex can exploit this to determine which slot is configured for startup via the [[https://github.com/mgcaret/davex-mg-utils/blob/master/iie.card.s#L118|dispslot routine]]. | ||