RE: Hübner & Worm Hard-Disk 24MB for PET

> PS: Now someone have to convert the code to 6502 assembler for the 8250 to use subdirectories ;)

I think that would be more work than writing it from scratch. I implemented it in my CBM-HD project, a 1541 with HDD onboard. A subdirectory is nothing more then another file but its layout is just like a normal directory. In my case its first file is the well known ".." which has two purposes: 1) the user can see it is a subdirectory and 2) I can store the information of its parent directory here. If I need to store more files in this directory than the sector can store, another sector is added. In contrary to the root directory that uses a reserved track, the first free sector is added. The advantage: there is almost no limit to the number of files a subdirectory can contain. The "almost" is the size of the disk of course. IIRC the 1581 uses $85 for marking a file as subdirectory, I used $86.

Next you have to create equivalents of MD, CD and RD. MD is IMHO the most simple one: just create a file and give it the correct structure. RD can be simple as well: scratch the directory file if it is empty. It becomes more difficult if you want to add DELTREE like features. CD can be simple as well: it just changes the pointer to where the 8250 should start (if the subdirectory exists).

What pointer, you may ask? When you perform a DIRECTORY or LOAD "$",x then the drive automatically starts to look at the first sector of its directory track. This behavior has to be changed. You should tell it to load a pointer that on its turn points to the track/sector combination where the drive should start its search.

I hope this helps.


With kind regards / met vriendelijke groet, Ruud Baltissen

http://www.baltissen.org



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