Icky - Progress

Where Alpha builders can post pics and progress etc
czietz
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Re: Icky - Progress

Post by czietz »

From a WD floppy disk controller IC application note:
The Floppy Disk Interface can be divided into three sections: Motor Control, Write Signals and Read Signals. All of these lines are capable of driving one TTL load and not compatible for direct connection to the drive. Most drives require an open-collector TTL interface with high current drive capability. This must be done on all outputs [...].
czietz
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Re: Icky - Progress

Post by czietz »

From the BBC Master. The quality is poor, but notice a WD1772 and 7406 buffers:
master.PNG
master.PNG (13.17 KiB) Viewed 3514 times
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exxos
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Re: Icky - Progress

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czietz wrote: Thu Sep 27, 2018 11:37 am The Floppy Disk Interface can be divided into three sections: Motor Control, Write Signals and Read Signals. All of these lines are capable of driving one TTL load and not compatible for direct connection to the drive. Most drives require an open-collector TTL interface with high current drive capability. This must be done on all outputs [...].
Thanks I didn't see any mention of IO buffers... It seems its the 1K pull up being the main issue. Though 40mA pull down on the LS06, vs 16MmA on a 04.. drives must need a lot of IO juice...
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Re: Icky - Progress

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exxos wrote: Thu Sep 27, 2018 10:24 am It might be worth scoping out some pins around ACIA area, such as (U54) A1 pin 11, A2 pin 8, (U32) pin 3 SNDCS.. (IC2 MFP) pin 48 CS.
Back to the plot...

My thoughts here are the chip select lines having noise on them causing the ACIA,YM etc not to be selected properly..

It is only a theory. Though I mention it as the GLUE on the original STFM is basically in the centre of the motherboard so the signals are not going as far to the chips on those boards...

However on the remake board, the GLUE about as far away from the ACIA,YM etc as it could possibly be.. So I am making the assumption that the signals have some noise is causing the odd issues..

So if someone can scope out the signals and upload them, then it will help..

Worst case with this issue is just adding some resistors in series with the CS signals.. Though I pretty much already anticipated this problem..
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PhilC
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Re: Icky - Progress

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Just wired the drive in on mine. It's detected but doesn't work. The disk activity light stays on, like the cable is the wrong way round.

Using one of your 1.44mb drives.

Anything obvious you can think of?
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Re: Icky - Progress

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Forgottenmyname wrote: Thu Sep 27, 2018 5:24 pm Just wired the drive in on mine. It's detected but doesn't work. The disk activity light stays on, like the cable is the wrong way round.

Using one of your 1.44mb drives.

Anything obvious you can think of?
Have you put the cable in upside down ? still need to do that...
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Re: Icky - Progress

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Yes I did but it doesn't detect the drive then
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Re: Icky - Progress

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Forgottenmyname wrote: Thu Sep 27, 2018 5:41 pm Yes I did but it doesn't detect the drive then
can you try a 720 drive ?
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Re: Icky - Progress

Post by PhilC »

Yes, I tried the one from my Mega and another from the STFM, both the drive lights stay on with cable one way and the other way the drive is not detected.

Just checked connections between 1772 and LS06 and they seem to be ok so far.
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Re: Icky - Progress

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Forgottenmyname wrote: Thu Sep 27, 2018 6:06 pm Yes, I tried the one from my Mega and another from the STFM, both the drive lights stay on with cable one way and the other way the drive is not detected.
Have to check pin 20 of the 1772 (motor on) and see if its doing anything... I dont know offhand if it goes high or low, but after desktop it should switch as normally the motor turns off once it gets to desktop.

Might also be worth testing the DMA, 1772, YM chip in your MEGA and make sure they work OK in another machine..
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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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