Has anyone else read through the disk, sector, and file format section of the TPDD software manual? I’m not sure if it’s glossing over some key information or if I’m just not understanding something. Most of my confusion is surrounding the sector ID field.
This is an explanation of my understanding of this with my assumptions and questions interspersed: The directory on track 0 sector 0 consists of a space management table and file control blocks (FCBs) for up to 40 files. The info for an FCB contains filename, attributes, file size, sector start, and sector end. Sector start and end values are not numbered from 0 to 79. Instead those bytes consists of 7 bits for track number (0-39) and one bit for sector number (0 or 1). I’ll call this “track, sector” notation, although I think “sector” is probably the MSB. For every sector, there’s an ID section and a data section. The ID section includes sector number. It’s not clear if the format for sector number is “track, sector” such as in the FCB in the directory, or if it’s simply a 0 or 1, or if it’s a continuous count such as 0, 1, …, 79. Any thoughts? The ID section also includes sector length. Not file length, sector length. Isn’t that just a fixed number of bytes for all sectors? What could this actually mean? The ID section also includes a “logical sector length code”. Once again, I’m not really sure what this means. The data section for track 0, sector 0 contains the directory, but for the rest of the sectors the data section contains space for file data. To access a file, the FCB in the directory can be used to access file name, length of file (length-1 for text, but for basic file maybe it’s the true length?), sector start, and sector end. The example in the manual (figure 1-9) shows a file which spans three sectors which are not in order physically on the disk. The file head sector pointer from the FCB takes us to the start sector for the file data. The diagram in Figure 1-9 claims that information in the sector ID field for the file’s first sector will tell us the sector number for the next sector of our file, and so forth until maybe the last sector ID field uses “0xFF” as the next sector pointer to act as a terminator? No where in the sector ID format section of the manual do I see where these “next sector pointers” exist. I have unanswered questions about this sector ID field above, so maybe that’s where I’m missing something. Any thoughts? Regards, Royce Sent from my iPhone > On Mar 20, 2025, at 06:31, Brian K. White <[email protected]> wrote: > > On 3/20/25 08:00, James Reed wrote: >> Hi >> Now I have the serial port working I'm wanting to move on to some new >> challenges. >> I had a Tandy 102 and TPDD (I think v1) many years ago, and I wrote a few >> programs that I'd like to get access to. I still have the floppy disk and >> now a Tandy 102 but I don't have the TPDD. >> I have a Greaseweazle and can make an image of the disk, but what I can't >> work out is how I can make use of this. All the utilities I've looked at >> seem to need you to have the actual hardware to read or write images, and I >> can't see any utilities which can extract the actual files. >> I'd be grateful for any pointers or if anyone can suggest anything. >> James > > fluxengine has support for it, and can use the greaseweazel hardware. > I have not tested it. > > https://cowlark.com/fluxengine/doc/disk-fb100.html > > This will only get you raw sectors not files, but the disk format is well > documented in the software manual, and there are only 40 tracks on the whole > disk, so, you can piece the files back together manually. > > http://tandy.wiki/TPDD#Documentation > > https://archive.org/details/tandy-service-manual-26-3808-s-software-manual-for-portable-disk-drive/page/n5/mode/2up > > It won't be exactly trivial, but I think there are no secrets making it > impossible. > > If you want to risk snail-mailing it, I'll just read it in a real drive if > you want. > > -- > bkw
