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Format with write protect on...

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    Format with write protect on...

    I wonder if anyone has seen this before. I fixed the optical sensors (write protect and index) on my Tandy 1000 teac drive, and it will give a write protect error if I try to delete a file, but format does not fail immediately. It goes through the motions like it is formatting, but at the end when it tries to write the fat/directory, THEN it fails with a write protect error. Does the same thing with 3.20 or 6.22. I tried a similar action on another PC and it fails immediately. It makes me wonder if it is a floppy controller IC level difference where the one used in the Tandy allows a format command without returning an error or something. The disk is NOT formatted though. It goes through the motions, but in the end, all the file data is still present.

    #2
    I tried to duplicate this on a Tandy 1000 w/ 360k drives, but the format is rejected at the start on my system. In my case, the format tool is presenting as "TANDY 1000 FLOPPY FORMAT VERSION 02.11.01". I also tried with MS DOS format and it rejected at the beginning as well.

    I'm curious what model Tandy 1000 is giving you this behavior?

    Comment


      #3
      It is a Tandy 1000A.

      The drive itself if a teac fd-54b-02-u.

      I did have to fix the drive - both of its optical sensors were bad. The result was it always thought the light was shining on it when it wasn't. For the write protect this meant it always thought it was non write protected, and for the index sensor this meant it always thought the light was shining through the hole in the disk. I replaced both sensors with an OPL-530 and it can now format and it also respects the write protect if I try to write to a disk, it is just this format oddity that is still strange.

      I've also got a GoTek hooked up so I am going to write protect one of the images on it and try to format it and see what happens.

      Comment


        #4
        It does the same thing with the GoTek. Goes through the motions of formatting, but the little LED segment that lights up for writing never lights up at all. At the end it goes to write and complains about write protect. Get out of the format and all the data is still there, you can execute programs off of it so no format is occurring. Not a drive issue then.

        Comment


          #5
          Nope, sounds like an FDC quirk to me. Apparently the FDC doesn't error out on format if the write protect is active.

          Comment


            #6
            Technical manual says it is an Intel 8272A.

            Comment


              #7
              Same as a NEC D765, then.

              Comment


                #8
                Well, the floppy stopped spinning. It seems the motor signal is no longer outputting for some reason. It was working fine with the GoTek and the not. I think I have another floppy IC around here from building a zeta2, I'll have to see what it is and see if it is a drop in replacement to try.

                Comment


                  #9
                  The question is, does it actually do a format with the write protect on or just the steps. Usually the write protect usually does two things. The drive sets a bit on the interface and physically block the disk from writing.
                  The firmware may not be looking at the interface or even looking to ensure the disk has been changed until that point in the code. I would not be surprised with this action.
                  Dwight

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                    #10
                    If WRITE GATE\ on the drive isn't enabled (i.e. pulled low), the drive will not write anything, no matter how the other signal lines twitch. It's an easy way to make a drive read-only--just break the WRITE GATE/ line (pin 24) and pull it high on the drive. You can easily do this with a SPDT switch and a resistor.

                    Write-protect status is available only upon completion of a command in status word 3. A "SENSE DRIVE STATUS" (04) command will suffice to get it without actually attempting to do anything.
                    Last edited by Chuck(G); April 3, 2021, 09:07 AM.

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                      #11
                      It doesn't not actually format the tracks, it just goes through the motion like it is. All the file data is still there and I was doing a /U option type format.

                      Comment


                        #12
                        Sounds as if your controller/driver combo isn't pulling WRITE GATE/ low.

                        Comment


                          #13
                          It formats/writes fine if there is no write protect.

                          Comment


                            #14
                            So the FDC isn't getting the message, obviously.

                            Comment


                              #15
                              That is what I think; other FDC's inform DOS that a disk is write protected when they try to format, but I don't think this particular FDC does.

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