SuperCard Pro Flux Image format (.scp)

[admin]

Your assumptions are correct. However, what you call "no flux areas" are actually really long flux transitions, and yes, they can be very long or very short and in groups as well. For example, it's not uncommon to see multiple flux transitions that are 22,000us to 27,000us on weakbit protected disks. The PC disk controllers do return a time duration, even if it is invalid so there really is no such thing as a "no flux area". That area will return random bit cell times each time read, but these all add up to the correct time. So, the bit cell position in reference to the index mark is the total time accumulated up to the point of interest. You can see in my visualizer data there is a total bit length in bytes and a total time of all of the bit cells added together. That time should match the index to index time within a few microseconds, depending on drive speed variations.

What you show in your data is not a no flux area, otherwise you would have no mid/high flux patterns shown like you do. Even if you turn on the erase head and output a 0 or a 1 to the disk, it is going to return flux transitions when the disk is read. Will they be correct? No, but they will be there as random transitions due to how the drive controllers function. Of course, this is somewhat drive controller specific as they all do slightly different things. Some drives return a long series of super short transitions, some return super long transitions, and some return about 25% more than longest possible bit cell duration.

I just noticed that the spec info attached to the original post is very outdated and changed some. Please see the new spec (now as a download).