Alien Syndrome (Arcade)
This game has debugging material.
Alien Syndrome is a top-down fast-paced action game where players must rescue hostages while shooting at aliens.
This screen is accessible in service mode after the memory test finishes. Normally a branch instruction prevents it from running, but the following patch NOPs it out so it is accessible again:
Set: aliensyn maincpu.mw@1C60E=4E71 maincpu.mw@1C610=4E71
The object display screen allows you to cycle through sprites (PAT NO), palettes (COL NO), orientation (DIR NO), and adjust the palette color data.
|Input||Outside color editor||Inside color editor|
|Up/down||Jump to color editor||Move to adjacent digit|
|Left/right||Move to adjacent row||Move to adjacent digit|
|Button 1/2||Adjust item by 1||Adjust item by 1|
|1P Start/2P Start||Adjust item by 16||No effect|
|1P+2P Start||Show/hide object size overlay||Show/hide object size overlay|
|Service||Exit screen||Exit screen|
Sprites of interest
There are some Sega characters that make an appearance in the object list.
|PAT NO||COL NO||Description|
This screen is accessible in service mode after the memory test finishes. The game sets up a pointer to the code that runs this editor but overwrites it with the game's reset entry point during the memory test. The following patch redirects the branch that skips the object display screen to instead go to the character display screen.
Set: aliensyn maincpu.mw@1C610=08A8
On this screen character data is grouped into 64 tiles and four groups are displayed for 256 tiles total.
- Up/Down selects the group's palette to edit
- Left/right selects the digit to edit of a palette
- Button 1/2 adjusts the selected digit
- 1P/2P start advances the grouping by 256 characters
Leftover Source Code
Fragment of memory test source code at 0x1DCBE:
Return from memory test * ------ << memory_test >> ------ memotest: btst.b #_TESTSW,SWITCH0 beq.
Fragment of listing at 0x2BA56:
00961 00962 *Angle Get to Player (Enemy Bomb) ************************** 00963 * 00964
The Alien Syndrome series
|Sega Master System||Alien Syndrome|
|Commodore 64||Alien Syndrome|
|Game Gear||Alien Syndrome|
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