Common pitfalls: Difference between revisions
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(Created page with "Check your hardware before checking your code... =Unwanted resets= * Watchdog not written to fast enough * Misaligned word or longword read/write * RTS with wrong return address…") |
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| Line 2: | Line 2: | ||
=Unwanted resets= | =Unwanted resets= | ||
* Watchdog not written to | * Watchdog not written to often enough | ||
* Misaligned word or longword read/write | * Misaligned word or longword read/write | ||
* 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 | |||
=Invisible sprites= | =Invisible sprites= | ||
* Sprites are disabled (NeoGeo CD only | * Sprites are disabled (NeoGeo CD only) | ||
* The [[fix layer]] is filled with non-transparent tiles and hides everything | * 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 ([[Sprites|SCB3]]). | ||
* Sprite tiles are all transparent (bad tile numbers ?). | * Sprite tiles are all transparent (bad tile numbers ?). | ||
* Shrinking values too low (should still be visible) | * Shrinking values too low (few pixels should still be visible). | ||
* Bad [[C ROM]], it happens... | * Bad [[C ROM]], it happens... | ||
* [[Palettes|Reference color]] (0) is not black. | * [[Palettes|Reference color]] (0) is not black. | ||
=Invisible fix layer= | =Invisible fix layer= | ||
* Fix is disabled (NeoGeo CD only | * Fix is disabled (NeoGeo CD only) | ||
* 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. | ||
| Line 24: | Line 25: | ||
=Wrong colors= | =Wrong colors= | ||
* Reference color (0) is not black. Set $400000 to #$8000. | * Reference color (0) is not black. Set $400000 to #$8000. | ||
* Palettes | * Palettes loading routine is broken. | ||
* Tiles are assigned to an uninitialized palette. | * Tiles are assigned to an uninitialized palette. | ||
| Line 32: | Line 33: | ||
=Erratic sprite movement= | =Erratic sprite movement= | ||
* Sprite is driven by the previous one. | * Sprite is driven by the previous one. | ||
* VRAM writes | * VRAM writes too fast. | ||
=Interrupts don't work= | =Interrupts don't work= | ||
Revision as of 02:08, 6 May 2011
Check your hardware before checking your code...
Unwanted resets
- Watchdog not written to often enough
- Misaligned word or longword read/write
- RTS with wrong return address in stack (or bad SP ?)
- JSR to BIOSF_BOOTSCR ($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 (0) is not black.
Wrong colors
- Reference color (0) is not black. Set $400000 to #$8000.
- 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 ?).
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.
- Interrupt mask cause 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.