[Coco] Fd-502 almost working.

[Robert Gault]

Walter,

Even if your controller and drive are perfect, unless you make changes to Disk Basic and ensure the 
NitrOS-9 drive descriptors are as required, you will not be able to read the back side of a disk.

For example, in Disk Basic 1.1 there is a drive table at $D89D-$D8A0: 1,2,4,$40 . With these values, 
only one side of a disk can be read. If you want to read both sides of each drive 0 & 1, the table 
must be changed to 1,2,$41,$42. Drives 2 & 3 become the back sides of drives 0 and 1.

  Now if you are using HDBDOS the double side format probably is used. With a standard Coco disk 
ROM, you will have to POKE the double side values into the table.
  NitrOS-9 in rb1773desc.asm has "Sides set 1". But you also have the dmode option of setting
"sid = #" where # can be 1 or 2. This does not force a two sided read but will permit it if the disk 
LSN0 indicates a double sided disk.
  The command Format permits you to select creating a 1 or 2 sided disk.

Robert

Walter Zambotti wrote:
> Hi guys.
>
> I managed to get my 40(2) track fd-502 working with my controller.
>
> Well half working.
>
> I can now read one side of my double sided disks.
>
> So i can start an os9 boot but it eventually fails when it trys to read the other side.
>
> Tried every jumper combo imaginable but I couldn't get the second side to read.
>
> I know the os9 disk has the correct driver and descriptor for 42 track double sided access.
>
> So one step closer but no cigar yet.
>
> Walter
>
> I took the fd controller board from the chinon fd-502 that had the faulty
>
> Sent from my Xperia by Sony smartphone
>