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My floppy remapper project, version 2

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    #16
    Ok, George, you knew this was coming. After using this solution for a bit, I do have a request.

    Most of my floppy work on the 4D will be using the HxC on the external floppy connector in the "2301" mode. However, every time I access my HxC, the motors on the internal floppy drives spin up. This is due to the common Motor Enable signal. In order to not abuse the original drives, it would be a great feature if the motor enable could be controlled, if not per drive, then at least on the internal floppy channel. ie. only trigger Motor Enable for the internal channel when one of the internal drives is accessed. I guess it would require another line from the board to the internal ribbon cable.


    Doable?
    Pete
    http://pski.net

    Comment


      #17
      Hah! Nice one. I think this would be a cool feature and it could be optional.

      One the model 3 and 4, all the signals are available (extbus and motoron) you just need an inverter and two AND gates to control motor-i and motor-e independently. There may be spare gates to do this on the 4d.

      To merge this into the remapper a pcb change would be needed, but it could be prototyped on the existing boards and needs a relatively small sw change.

      I would need two additional output signals, one each for motor-i and motor-e As I'm out of pins, I'd have to steal them from the leds.

      Also, I'm out of clc blocks, I'd have to drive the motor pins via sw. This means there may be a couple of microsecond delay when turning on the motors. I assume this is probably ok. As a bonus, I can avoid spinning up the drives when I change the mapping too.

      I do wonder if there could be a problem copying from an internal drive to external drive. Would the floppy drivers handle the additional drive spin up time? This might be fixable in software as I could probably detect the drive to drive copy case.

      The 4p has only one motor control, so this would require a mod to the cable to separate the motor signal wire going to the external connector.

      Assuming none of these things are issues, it seems doable!

      George

      Comment


        #18
        Originally posted by pski View Post
        Ok, George, you knew this was coming. After using this solution for a bit, I do have a request.

        Most of my floppy work on the 4D will be using the HxC on the external floppy connector in the "2301" mode. However, every time I access my HxC, the motors on the internal floppy drives spin up. This is due to the common Motor Enable signal. In order to not abuse the original drives, it would be a great feature if the motor enable could be controlled, if not per drive, then at least on the internal floppy channel. ie. only trigger Motor Enable for the internal channel when one of the internal drives is accessed. I guess it would require another line from the board to the internal ribbon cable.


        Doable?
        Actually, if you want per drive control, I think this may be fairly straightforward, without any changes to the remapper board.

        Take the following as unverified, I've yet to try this...

        In the Tandon TM-50 service manual (for my Model 4P), and it looks like there are some jumpers to do exactly what you want. There is a jumper to disconnect pin 16 (N-Motor-On) (W1 on the motor control board) and a jumper block (U19) "MTR SEL" to control Motor-On using the Drive Select line.

        On older drives, the same change may be possible with a minimal mod (i.e. jumper wire) on each drive (as far as I can tell from the schematics). I think you need to be careful of the termination resistors to make sure you don't modify the termination value.

        I still worry that doing this may have some unintended side effect (or failure mode) when copying from drive to drive.

        If your Model 4D has Tandon TM-50-2 drives, this could be exactly what you want.

        George

        Comment


          #19
          It may be best if I just rig up a manual switch on the internal motor line.
          Pete
          http://pski.net

          Comment


            #20
            Here's an update on my final configuration. I rigged up 2 switches. One switch is for the floppy remapper enable/disable circuit. The second switch is on the internal floppy drive 12v power line. This allows me to turn off the internal drive motors when using the HxC on the external floppy channel which I plan to do 95% of the time.

            IMG_2907.jpegIMG_2908.jpegIMG_2909.jpeg

            I like to joke that it makes my M4 look like another one of my favorite computers, the SuperPET.

            commodore_mmf9000-cbm_8050_2.jpg
            Pete
            http://pski.net

            Comment


              #21
              I would like to get one of these boards but need a little guidance on dealing with PCBWay. I really cannot make sense of their web site. Was able to find the remapper board, but from there it's unclear how to order an assembled unit.

              Comment


                #22
                If you just want one, pm me and I'll hook you up. I have two left.

                Comment


                  #23
                  OK - so I have a question... I have a Gotek and I would like to use it as an external drive and be able to boot from it.
                  So why couldn't I just modify the floppy cable to piggy back another termination to the external Gotek configured as device 0
                  then just use a switch to turn off power alternatively between the Gotek and the TRS-80 drive?
                  flip the switch to TRS-80 and Gotek goes off and TRS-80 drive is on - boot from it or do whatever.
                  Want to switch to the Gotek, flip the switch, Gotek turns on and TRS-80 drive turn off.

                  Am I missing something here why this wouldn't work?

                  Comment


                    #24
                    Originally posted by NoPizzaTonite View Post
                    OK - so I have a question... I have a Gotek and I would like to use it as an external drive and be able to boot from it.
                    So why couldn't I just modify the floppy cable to piggy back another termination to the external Gotek configured as device 0
                    then just use a switch to turn off power alternatively between the Gotek and the TRS-80 drive?
                    Because external connector does not have drive select signal for drive 0.

                    Comment


                      #25
                      Hi George,

                      I wouldn't be using the external connector. I am expanding the internal floppy ribbon with another device. The ribbon would continue out through the opening at the bottom of the computer.
                      So, I would have two device 0: on the same cable (internal and external) and contention would be eliminated by switching the power on/off on each.

                      Comment


                        #26
                        Hi nopizzatonight,

                        Yes, I think that should work. I'm not sure if you'd need to switch both 5v and 12v power, or just the 5v. Alternatively, you can wire up a switch for the single drive select 0 line (since you are making a new cable) instead of messing with power.

                        Comment


                          #27
                          Thank you - you are right LOL - don't know why I was over-complicating it with power.

                          In the end I 3D printed a face plate for my Gotek and put a switch on it to alternate between the top drive and the Gotek below alternately as drives 0: and 1:
                          I saved the bottom drive as a spare in case something ever goes south with the drive currently in the system


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