galibert
commented
3 years ago I don't know that hardware (I know the following ones), but Konami tends to follow a line of design. In the later ones there can only be one sprite per priority level because that level tells the chip where to write the sprite data in its internal sprite ram (we don't emulate that correctly, partially because we don't emulate that part of the tbyahhoo protection correctly), and sprites with the lowest priority level (0 or ff, depending on a register) are ignored. Could there be something similar going on?
OG.
On Thu, Apr 15, 2021 at 6:28 AM Furrtek @.***> wrote:
Sprites forming the digits of the countdown timer aren't cleared properly after pressing start when it shows 10. Shown here: https://mametesters.org/view.php?id=401
I tried simplifying how the sprite RAM is handled to reflect how the real chip works (no buffer copying involved) but it didn't solve the issue.
The CPU maintains a sprite list starting at 0x1200 in RAM, which is used to generate the sprite RAM data for k007121_2 each new frame. The first few entries seem to always be used for P1's sprite and bullets. When the countdown timer starts, those entries are overwritten by several 8x8 sprites to form the digits.
If the player presses start when the counter is below 10, P1's sprites overwrite enough of the entries to clear the single digit. However if the player presses start at 10, more sprites are used so P1's sprites aren't enough to clear both digits. Firing or jumping causes P1's sprite list to expand for a moment, effectively clearing the remaining sprites.
It seems that the CPU is rewriting the garbage sprites, since they reappear even if the k007121_2's sprite RAM (0x5000~0x5FFF) is cleared manually. So the bug might not be related to the k007121.
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furrtek
smf-
Sprites forming the digits of the countdown timer aren't cleared properly after pressing start when it shows 10. Shown here: https://mametesters.org/view.php?id=401
I tried simplifying how the sprite RAM is handled to reflect how the real chip works (no buffer copying involved) but it didn't solve the issue.
The CPU maintains a sprite list starting at 0x1200 in RAM, which is used to generate the sprite RAM data for k007121_2 each new frame. The first few entries seem to always be used for P1's sprite and bullets. When the countdown timer starts, those entries are overwritten by several 8x8 sprites to form the digits.
If the player presses start when the counter is below 10, P1's sprites overwrite enough of the entries to clear the single digit. However if the press happens at 10, more sprites are used so P1's sprites aren't enough anymore to clear both digits. Firing or jumping causes P1's sprite list to expand for a moment, effectively clearing the remaining sprites in a few steps.
It seems that the CPU is rewriting the garbage sprites, since they reappear even if the k007121_2's sprite RAM (0x5000~0x5FFF) is cleared manually. So the bug might not be related to the k007121.