jumper settings for Chinon FZ-354 floppy

Hello all, I finally set up my SWP ATR8000 last night. This device allows an Atari computer to use standard floppy drives along with Atari proprietary drives. Included with the ATR8000 was an external floppy case with power supply that can hold 2 half height 5 1/4 floppies. It had 1 Shugart SA455 5 1/4 DSDD drive and I added (after hours of drilling and filing) a Chinon FZ-354 3 1/2 DSDD. I put the Chinon on the end of the cable set at drive 3. I removed the resistor pack from the Shugart and added a switch using old motherboard cables so I can change the drive id from 1 to 2. This is so I can boot CP/M from the Shugart as drive 1 or switch it to drive 2 and boot from an Atari drive. I had no trouble using the Shugart drive but the Chinon gave me a lot of problems. After a little research on the net, I changed the jumper from DC to RDY (this sounded like the answer) but I still got errors. The errors occurred after I rebooted and wrote to the same disk. Every file from the second write was messed up. The only jumpers left were MM and MD so I changed the jumper from MM to MD and it works great now. My big question is what are the MM and MD settings for, and how did this solve my problem? From what I've read, 3 1/2 drives don't have removable resistor packs and they somehow achieve termination automatically so that's why I put the Chinon at the end of the cable. Thanks for listening to my raving. By the way, does anyone have the CP/M disks for this setup for sale or for trade? Ralph