MPF F11W floppy write protect issue (STE)

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ijor
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Re: MPF F11W floppy write protect issue (STE)

Post by ijor »

exxos wrote: Fri Dec 07, 2018 1:39 pm The WP signal is set on bit 7 of the status register. So when TOS reads it, it sees a false WP signal because of ringing on the bus..
Not bit 7, bit 6. But yes, TOS could see a false wprot error when reading the status register. But if so you would expect general floppy malfunction. Even if ringing affects just a single bit, most programs read from the floppy shouldn't work.
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Re: MPF F11W floppy write protect issue (STE)

Post by exxos »

ijor wrote: Fri Dec 07, 2018 1:53 pm Not bit 7, bit 6. But yes, TOS could see a false wprot error when reading the status register. But if so you would expect general floppy malfunction. Even if ringing affects just a single bit, most programs read from the floppy shouldn't work.
I was having read issues, also write issues hence the corrupt desktop.inf file causing chaos on my desktop, obviously different issue then WP signal not working correctly as the write happend. I would assume read issues would have been partly fixed by CRC checks. Though I never looked into how all the CRC works.

The problems are very intermittent. Like one wrong bit every 60 seconds. If reading a floppy then people in general may not even notice the problem. Though if formatting floppies, or saving files a lot, then as I pointed out, corruption happens then it is realised.

I was simply illustrating that the ringing as a particular plausible cause of failure. If anything it proves there is something "wrong" happening. Indeed if the ringing was bad enough it could falsely register as the wrong logic level. Of course it will be difficult to capture that. Ringing could actually be a lot worse than is even visible. Indeed it would be very problematic to capture A minute's worth of data exactly see when the faults happen.

The bottom line is that a problem was identified, the solution was to add the pullups. This cleaned up the signals immensely and the problem went away.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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ijor
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Re: MPF F11W floppy write protect issue (STE)

Post by ijor »

exxos wrote: Fri Dec 07, 2018 1:57 pmI was having read issues, also write issues hence the corrupt desktop.inf file causing chaos on my desktop, obviously different issue then WP signal not working correctly as the write happend.
oh, I see.
I would assume read issues would have been partly fixed by CRC checks.
No, CRC is something between the disk, the drive and the FDC. CRC doesn't protect transactions on the data bus. The data bus is assumed to be reliable.

Edit: typos
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andresv
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Re: MPF F11W floppy write protect issue (STE)

Post by andresv »

I think I'm having these exact same problems with my floppy drive.
When formatting in GEM, when finishing if fails.
The floppy seems to read without any problems, but it cannot write anything and complains with "disk is write protected", when is not.
I have RECAP my PSU, that seems not to be the problem. But voltage is a little higher (5.2V) and was wondering if need to regulate the PSU to a little lower value. If that's the case, what voltage would be better / correct?

Is there a way to confirm the issue with the noise at the data bus? How I can be sure that adding the resistor pullup on the WD will solve this issue?

This issue with noise on the data bus would also affect the DMA (hard disk) transfers?

How these machines worked as new? Something should have degraded or broke over time that is causing this data bus noise. What could be the cause then?

Thanks!

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Re: MPF F11W floppy write protect issue (STE)

Post by exxos »

I suggest you do all the mandatory fixes for your machine to get it to the best working state.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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People should find solutions to problems, not find problems with solutions.
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andresv
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Re: MPF F11W floppy write protect issue (STE)

Post by andresv »

Perfect, I will do all mandatory fixes but I have a couple questions.

List of mandatory fixes: https://www.exxosforum.co.uk/forum/viewt ... =17&t=1585

Mandatory fix #3: talks about adding 10k pullups on the DMA data bus.
There are two links in that topic, one talks about adding a 10k resistor pack on the 1772 floppy controller, this is pretty clear to me I have to do this.
The other link talks about issues with booster cards, and I don´t have one so I think those comments don´t apply to my case.

Mandatory fix #4: talks about adding 1k resistors on the 7404 connected to the WD1772.
Those 1k resistors are needed IN ADDITION to the 10k pack on the data bus from #3?

Mandatory fix #12: resistor bus, no problem, I think that´s clear.

So in my case I would need to perform these three fixes. I don´t see any video ghosting and I don´t have any problems with reset so far.

Additional question: could these write issues have something to do with the EPSON SMD-380 drive I have?
There is some instructions on how to test (maybe I can connect the Atari floppy drive to a PC to test it) and refurbish this drive?
I have found instructions for other drive models but not for the 380.

Thanks!

Andres.
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Re: MPF F11W floppy write protect issue (STE)

Post by exxos »

andresv wrote: Tue Aug 17, 2021 3:00 pm Mandatory fix #3: talks about adding 10k pullups on the DMA data bus.
There are two links in that topic, one talks about adding a 10k resistor pack on the 1772 floppy controller, this is pretty clear to me I have to do this.
The other link talks about issues with booster cards, and I don´t have one so I think those comments don´t apply to my case.
The fix needs doing with or without a booster. The problems are just more visible when a booster is fitted.
andresv wrote: Tue Aug 17, 2021 3:00 pm Mandatory fix #4: talks about adding 1k resistors on the 7404 connected to the WD1772.
Those 1k resistors are needed IN ADDITION to the 10k pack on the data bus from #3?
They are for different parts of the circuit, they both need doing.
andresv wrote: Tue Aug 17, 2021 3:00 pm Additional question: could these write issues have something to do with the EPSON SMD-380 drive I have?
There is some instructions on how to test (maybe I can connect the Atari floppy drive to a PC to test it) and refurbish this drive?
I have found instructions for other drive models but not for the 380.
Like I said earlier, there could be multiple reasons for the failure, the drive itself should be really where you are starting and try a known working one first.

I don't personally know much about original drives, I only really use the MPF920 these days.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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