exxos's Atari, Amiga & retro forum

I've finally decided to try and fix my Mega ST floppy controller etc.

I've had a look at the dataset for the Wd1772, ym2149 and the 68901 and have an idea how they work.

So for clarity, the floppy motor comes on when clicking the floppy icon but shortly after it tells me there's an issue with the disk, damaged etc.

So I get a blip on the interrupt req pin on the wd1772, 28 IIRC but im expecting R/W and /CS on the WD1772 to go low to enable reading, or at least this im presuming.

/CS goes yo /FDCS on the DMA but I don't have a clue where the go signal for FDCS comes from exactly.

I do know that you get an interrupt request from the 68901 and this goes through the 74LS02 and to the YM2149 but am struggling a bit from there. I also know that BC1 changed over when looking for a disk.

Could someone please give me a couple of pointers re the DMA and FDCS stuff.

Thanks.

@PhilC

If I remember the 2149 address lines 3 of them are used to select drive ds0 or ms0 cant Remember.

Tom