Dragon World 2 PGM Protection Issue

[RetroHQ]

MAME version

0.269 (mame0269)

System information

N/A

INI configuration details

N/A

Emulated system/software

PGM / Dragon World 2 (drgw2)

Incorrect behaviour

On Dragon World 2 if you insert a credit and start the game and just leave the timer to run out you get a hang. This looks similar to the IGS025 error screens you get with DRGW3, although with static rather than random tile positions.

Expected behaviour

No hang.

Steps to reproduce

Start mame (mame drgw2)
Insert coin
Select beginner
Wait for timer to run out

Additional details

No response

[Robbbert]

Confirmed with current git, although the screen changed to a bunch of brown fruit tiles then hung up.

Could be similar to https://mametesters.org/view.php?id=7737

Just like in that report, could be a protection issue.

[RetroHQ]

I've just confirmed it's the IGS025,

When in game put a watch on the IGS025 registers --

wp d80000,4,r

After the time up message you'll get a break at 1211F2 with D0=3FC5 (so prothold C5)

The code generating the comparison value comes up with 45, not C5. Manually setting D0=C5 at 121308 allows the game to continue.

I've just been debugging this type of protection on the PGMGD for DW3 so I'll see if I can fix it while it's fresh in my mind.

[RetroHQ]

I think this is an ASIC12 issue rather than IGS025 after all. The prothold values as calculated (80cb7e) and checked don't make sense. The hilo value (80cb7a) is set once and the initial value for prothold is junk. There is another more sensible looking prothold also calculated (80cb8a) along with properly updated hilo (80cb86) but the values written to the IGS025 dont make sense given what's being tracked. My only conclusion is the code path is wrong somewhere due to an ASIC12 issue.