Common pitfalls: Difference between revisions
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=Unwanted resets= | =Unwanted resets= | ||
* Watchdog not written to often enough | * [[Watchdog]] not written to often enough | ||
* Misaligned word or longword read/write | * Misaligned word or longword read/write (generates an [[68k error handling|Address error]]) | ||
* RTS with wrong return address in stack (or bad SP ?) | * RTS with wrong return address in stack (or bad SP ?) | ||
* JSR to BIOSF_BOOTSCR ($C00438) instead of JMP | * JSR to BIOSF_BOOTSCR ($C00438) instead of JMP | ||
| Line 21: | Line 21: | ||
* No non-transparent tiles mapped (bad [[S ROM]] ?) | * No non-transparent tiles mapped (bad [[S ROM]] ?) | ||
* Tiles are on the invisible borders. | * Tiles are on the invisible borders. | ||
* Reference color | * Reference color is not black. | ||
=Wrong colors= | =Wrong colors= | ||
* Reference color | * Reference color is not black. | ||
* Palettes loading routine is broken. | * Palettes loading routine is broken. | ||
* Tiles are assigned to an uninitialized palette. | * Tiles are assigned to an uninitialized palette. | ||
| Line 30: | Line 30: | ||
=Shrinked sprites show garbage below them= | =Shrinked sprites show garbage below them= | ||
* The unused part of the sprite maps isn't cleared with a transparent tile (hardware glitch ?). | * The unused part of the sprite maps isn't cleared with a transparent tile (hardware glitch ?). | ||
* Bad sprite size (too tall). | |||
=Erratic sprite movement= | =Erratic sprite movement= | ||
| Line 37: | Line 38: | ||
=Interrupts don't work= | =Interrupts don't work= | ||
* Some emulators ignore the [[68k interrupts|raster line interrupt]], it may work on the real hardware. | * Some emulators ignore the [[68k interrupts|raster line interrupt]], it may work on the real hardware. | ||
* | * The interrupt mask causes them to be ignored by the 68k. Check the SR register. | ||
* Wrong configuration of the raster line interrupt, see [[Memory mapped registers|'''REG_HBLANKCNT''' ($3C0006)]]. | * Wrong configuration of the raster line interrupt, see [[Memory mapped registers|'''REG_HBLANKCNT''' ($3C0006)]]. | ||
* The interrupt vector points to an RTE or RTS. Beware of the different levels between cart and CD systems. | * The interrupt vector points to an RTE or RTS. Beware of the different levels between cart and CD systems. | ||
| Line 44: | Line 45: | ||
* Check the "NEO-GEO" string at 0x100 | * Check the "NEO-GEO" string at 0x100 | ||
* Check the security code at (0x182).l | * Check the security code at (0x182).l | ||
[[Category:Code]] | [[Category:Code]] | ||
Revision as of 22:28, 25 May 2011
Check your hardware before checking your code...
Unwanted resets
- Watchdog not written to often enough
- Misaligned word or longword read/write (generates an Address error)
- RTS with wrong return address in stack (or bad SP ?)
- JSR to BIOSF_BOOTSCR ($C00438) instead of JMP
Invisible sprites
- Sprites are disabled (NeoGeo CD only)
- The fix layer is filled with non-transparent tiles and hides everything.
- Sprite position is out of the 320x224 visible area.
- Sprite size is 0 (SCB3).
- Sprite tiles are all transparent (bad tile numbers ?).
- Shrinking values too low (few pixels should still be visible).
- Bad C ROM, it happens...
- Reference color (0) is not black.
Invisible fix layer
- Fix is disabled (NeoGeo CD only)
- No non-transparent tiles mapped (bad S ROM ?)
- Tiles are on the invisible borders.
- Reference color is not black.
Wrong colors
- Reference color is not black.
- Palettes loading routine is broken.
- Tiles are assigned to an uninitialized palette.
Shrinked sprites show garbage below them
- The unused part of the sprite maps isn't cleared with a transparent tile (hardware glitch ?).
- Bad sprite size (too tall).
Erratic sprite movement
- Sprite is driven by the previous one.
- VRAM writes too fast.
Interrupts don't work
- Some emulators ignore the raster line interrupt, it may work on the real hardware.
- The interrupt mask causes them to be ignored by the 68k. Check the SR register.
- Wrong configuration of the raster line interrupt, see REG_HBLANKCNT ($3C0006).
- The interrupt vector points to an RTE or RTS. Beware of the different levels between cart and CD systems.
Game don't boot (goes directly to the crosshatch)
- Check the "NEO-GEO" string at 0x100
- Check the security code at (0x182).l