[Coco] Reading floppies with CRC error?

[tim lindner]

Darren A <mechacoco at gmail.com> wrote:

> There is a known problem when using the 'Read Track' command of the Western
> Digital floppy controllers.  The address mark detector remains on during
> the entire operation. Certain byte sequences contained in the sector data
> will cause a false trigger. When this happens you end up reading clock bits
> instead of data.
> 
> The problem will arise with the following known byte patterns:
> - $29 and previous even byte
> - $52/$53 and previous byte dividable by 4
> - $A4 to $A7 and previous byte dividable by 8
> - $14 and following byte's first bit (MSB) set to 1

[Sorry for replying to such an old post]

This above as intridgued me ever since I've read it. So I decided to
hack Disk BASIC to read tracks and then use the CoCo SDC to writen them
to a "Big Floppy" for further study.

You'll find the program here:

http://www.macmess.org/downloads/trkcpy.dsk

It requires a CoCo 3, Floppy disk controller/drive, CoCo SDC, and
multipak.

This is interesting to me and may be interesting to others.

http://tlindner.macmess.org/?page_id=533

-- 
tim lindner
tlindner at macmess.org                                              Bright