TRS-80 Model II Fixed Disk Controller Support

On 1/8/2013 11:19 PM, John Ball wrote: I only have a guess, and recent postings also discuss it. I wonder if your lowlevel program is attempting to read an error map from the drive and failing? There were error maps recorded on many drives but controllers and programs seldom bothered to try to read them back and just blasted the entire track when doing a low level format. I would try to find a drive which hasn't been formatted and tested on a system which might have done this, and see where you get to. I know the problem existed with SMD drives. The manufacturers would record flaw maps on the drives and some controllers would read and use them. Most gracefully continued if the flaw map was not there, but some did not. We made a controller which overwrote the flaw maps, and used a novel soft sector format on the SMD drives to record, so we didn't actually need the flaw maps. We looked at a similar controller for the smaller drives, and it would have worked, but we never proceeded with the product. I don't know if that is your problem or how to verify that. I suspect the drive is left selected because the controller state machine hung up for some reason, and didn't transition back to an idle state. Another path to verify is whether you have the drive write protected or enabled, and whether the drive status as to whether it is write protected is properly brought back to the controller. thanks Jim