08435: trs80l2: WD1771 does not support a1 DAM status bit

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
08435	Core	Critical (emulation)	Always	Oct 15, 2022, 17:10	Oct 23, 2022, 09:20

Tester	pnp2084	View Status	Public	Platform	MAME (Official Binary)
Assigned To	galibert	Resolution	Fixed	OS	Windows 10/11 (64-bit)
Status [?]	Resolved			Driver	trs/trs80.cpp
Version	0.248	Fixed in Version	0.249	Build	64-bit
		Fixed in Git Commit	48eee89	Github Pull Request #

Summary	08435: trs80l2: WD1771 does not support a1 DAM status bit
Description	The attached zork25.mfi will not boot on trs80l2 because the WD1771 emulation doesn't support the "a1" DAM marker bit.
Steps To Reproduce	Run the trs80l2 driver with the floppy enabled: mame -w trs80l2 -flop1 zork25.mfi The disk will spin but no boot screen will appear. The DMK file source for the MFI will boot in trs80gp.
Additional Information	The problem is in wd_fdc.cpp. It is also a problem on write sector but this file won't test that. For the WD1771 chip the status check needs to look at fb,fa,f9,fa and set an additional status flag. Current code: if((cur_live.data_reg & 0xfe) == 0xf8) status \|= S_DDM; The WD1771 data sheets describe the proper behaviour fairly clearly: a1a0 mark 0 0 FB 0 1 FA 1 0 F9 1 1 F8
Github Commit

Flags
Regression Version
Affected Sets / Systems	trs80l2

Attached Files	zork25.zip (256,105 bytes) Oct 15, 2022, 17:10 Uploaded by pnp2084 Zork aventure game in MFI forwmat

No.20609 pnp2084 Tester Oct 17, 2022, 17:31	galibert has fixed the problem with these two commits: https://github.com/mamedev/mame/commit/b5a7c3025a14b4152e00b80d56f795ba1c924046 https://github.com/mamedev/mame/commit/48eee89e3cff2f5a1ce190904a457cc8c136be39
No.20610 Robbbert Senior Tester Oct 17, 2022, 23:04	Thanks for the feedback.