08511: trs80l2: SuperUtility 3 boot fails because of false sync

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
08511	Core	Major	Always	Nov 10, 2022, 01:09	Mar 30, 2023, 17:27

Tester	pnp2084	View Status	Public	Platform	MAME (Official Binary)
Assigned To	tlindner	Resolution	Fixed	OS	Windows 10/11 (64-bit)
Status [?]	Resolved			Driver	trs/trs80.cpp
Version	0.249	Fixed in Version	0.254	Build	64-bit
		Fixed in Git Commit	6ea69b0	Github Pull Request #	#11041

Summary	08511: trs80l2: SuperUtility 3 boot fails because of false sync
Description	The attached su3v30-perl.mfi (from the su3v30.dsk DMK file) fails to boot on the TRS-80 Model I. The problem is the RADDR commands see false FM 0xFE sync bytes in the MFM data of Track 1. As a result, the code retries the RADDR a few times until it fails. The following breakpoints can be used to see the RADDR results. bp 452d - $c0 RADDR bp 452a - see 4a00 (HL) accumulate bogus results The groups of 6 bytes at 0x4a00 are: "FE FE FF F2 B1 F5" - false "20 20 20 02 76 DE" - real "30 30 30 02 2D 69" - real "25 25 25 02 DE 9E" - real "E5 EF F5 C6 DE 77" - false "F3 F1 FE BE 5F 77" - false
Steps To Reproduce	The follow command will display "DIsk Error _" mame trs80l2 -flop1 su3v30-perl.mfi
Additional Information	Possibly the WD17xx state machine should enforce some "sync zero" bits before detecting the FM IDAM.
Github Commit

Flags
Regression Version
Affected Sets / Systems	trs80l2

Attached Files	su3v30.zip (293,565 bytes) Nov 10, 2022, 01:09 Uploaded by pnp2084 SuperUtility 3.0 for TRS-80 Model I

No.21129 galibert Developer Feb 28, 2023, 22:03	Ok, I now know how the wd fdcs detect FM special marks, and the current code is incorrect. I'll try to work on a fix.