[Coco] CoCo Emulator Floppy Images - JVC format

[tim lindner]

Eric J. Rothfus <eric at rothfus.com> wrote:

> Thanks Tim.  I've downloaded a couple of your "section
> H" examples.
> 
> What I meant by "deleted sector" is really a deleted
> data mark within the JVC...meaning that the image is
> using the extended "attributes" byte in the front of
> each sector.  Have any of those types of images?  I
> just haven't seen any "real" floppy images (made from
> real floppies) that have used the extended features of
> JVC.

Nope. I don't have any JVC images the use the deleted data mark feature
of JVC. I believe the game "The Sands of Egypt" uses a deleted data mark
for copy protection purposes, but that is the only disk I know about. I
have that disk in DMK, but never bothered to convert it to JVC.

> I'm looking to excersize JVC reading code that I have.
> This code is part of a larger project that I'm working
> on.  The goal is to be able to run floppy images easily
> on a physical vintage machine...including the CoCo.
> The system currently supports DMK pretty well...just
> wanted to make sure that it supports JVC correctly too.
> (http://www.theSVD.com)

Besides any software you wrote, I don't know of any software that
reads/supports the attribute byte of the JVC format.

Nathan Woods brought up a good point (a number of months ago) to me
regarding the attribute byte: It wont work!

If the file contains an attribute byte on each sector the the header
size calculation (file size mod 256) will give the wrong result.

Since I really like the whole "optional header" thing, I might just drop
the attribute byte from the document becuase it just doesn't fit.

Jeff Vavasour, are you reading this? What do you think of this
incompatibility?

> You mentioned in a previous posting the Diecom images
> that you've run on the emulator.  But those are in DMK,
> right?  In other words, JVC isn't expressive enough to
> represent them.

Correct.

***

Regarding your SVD project: Cool!

-- 
tim lindner
tlindner at ix.netcom.com                                            Bright