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Me Tarzan, you Jane....

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This commit is contained in:
RobertoFresca 2016-05-28 13:09:29 -03:00
parent 958731ef5a
commit cc87a10563
1 changed files with 7 additions and 7 deletions
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src/mame/drivers/magicfly.cpp
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@ -253,23 +253,23 @@
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After check the last bit of $1800, code jump into a loop ($DA30)...
After check the last bit of $1800, the code jumps into a loop ($DA30)...
BEHAVIOUR OF BOOT CHECK (magicfly):
1) Fill the video RAM with spaces (0x20), and color RAM with 0x15.
2) Check bit 7 of $1800 (video RAM, 1st offset) if activated.
1) Fills the video RAM with spaces (0x20), and color RAM with 0x15.
2) Checks bit 7 of $1800 (video RAM, 1st offset) if it's active.
3) If true, go to $DA30 (incremented fill infinite loop).
4) If not, fill the video RAM with spaces (0x20), and color RAM with 0x1F.
5) Check bit 7 of $1800 (video RAM, 1st offset) if activated.
4) If not, fills the video RAM with spaces (0x20), and color RAM with 0x1F.
5) Checks bit 7 of $1800 (video RAM, 1st offset) if it's active.
6) If not, go to $DA30 (incremented fill infinite loop).
7) If true, returns and continue to NORMAL GAME.
7) If true, returns and continues to NORMAL GAME.
Since bits 0-2 are for regular colors, seems that bit 3 in color RAM
(bit 2 for 7mezzo) is mirrored to bit 7 through a kind of device.
This is the only explanation I found to allow a normal boot, and seems to be
created as a protection method that don't allow owners to use a ROM-swap on
created as a protection method that doesn't allow owners to do a ROM-swap on
their boards, converting from one game to another.