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mg_notes:iie_card:weird_stuff [2017/08/06 03:26] M.G. [The Key Translation and the A register] |
mg_notes:iie_card:weird_stuff [2017/08/07 15:14] M.G. [Other Weird Instructions] |
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| ^ In Routine ^ Address ^ Code ^ Function ^ | ^ In Routine ^ Address ^ Code ^ Function ^ | ||
| - | | RESET | $FAB4 | $02 $02 | ? | | + | | PWRUP | $FAB4 | $02 $02 | ? (appears where standard %%//%%e has LDA #$C8 at beginning of boot slot search) | |
| - | | RESET | $FAC0 | $02 $03 | ? | | + | | PWRUP | $FAC0 | $02 $03 | ? (appears where standard %%//%%e has CMP #$C0 after decrmenting the slot pointer) | |
| | APPLEII | $FB63 | $02 $04 | Display copyright message on screen, disappears if screen scrolls. | | | APPLEII | $FB63 | $02 $04 | Display copyright message on screen, disappears if screen scrolls. | | ||
| | BELL1 | $FBDD | $02 $01 | Play system bell sound. | | | BELL1 | $FBDD | $02 $01 | Play system bell sound. | | ||
| - | | GETLN1 | $FD78 | $02 $06 | Key translation called right after rdchar. Converts A reg from <key>DELETE</key> to <key><-</key>. | | + | | GETLN1 | $FD78 | $02 $06 | Key translation called right after rdchar. If A reg has <key>DELETE</key>, converts it to <key><-</key>. | |
| + | | | | $02 $05 | Not found in firmware, yet, but presumably this exists. | | ||
| + | |||
| + | Hypothesis for $02 $02 and $02 $03: | ||
| + | |||
| + | $02 $02 loads the accumulator with $Cn+1 where n is the slot selected in the control panel, or $C8 for "Scan". | ||
| + | |||
| + | $02 $03 checks the accumulator and depending on the control panel setting either allows the loop to continue (scan and A > $C0), drops to BASIC (scan and A = $C0), or prints the "unable to boot" message (specific slot and A != $Cn). | ||
| ==== The Key Translation and the A register ==== | ==== The Key Translation and the A register ==== | ||
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| 88 is the code for the left arrow key. That's some serious magic, and in two bytes the Card converts <key>DELETE</key> to <key><-</key>. | 88 is the code for the left arrow key. That's some serious magic, and in two bytes the Card converts <key>DELETE</key> to <key><-</key>. | ||
| + | ==== The Two-Byte Copyright ==== | ||
| + | |||
| + | Try this sequence of instructions: | ||
| + | |||
| + | <code> | ||
| + | ]HOME | ||
| + | ]CALL -151 | ||
| + | *300:02 04 60 | ||
| + | *300G | ||
| + | </code> | ||
| + | |||
| + | Hit the left arrow a bunch of times until the display scrolls. **POOF!** | ||
| + | |||